The/at design/nn of/in a/at mechanical/jj interlocking/vbg frame/nn is/bez much/ql like/cs a/at mechanical/jj puzzle/nn ,/, but/cc once/cs understood/vbn ,/, the/at principles/nns can/md be/be applied/vbn to/in any/dti track/nn and/cc signal/nn arrangement/nn ./.
In/in the/at frame/nn are/ber two/cd sets/nns of/in bars/nns which/wdt interact/vb with/in each/dt other/ap to/to prevent/vb the/at operator/nn from/in making/vbg dangerous/jj moves/nns ./.
The/at main/jjs set/nn of/in bars/nns are/ber the/at ``/`` tappets/nns ''/'' and/cc one/cd tappet/nn is/bez connected/vbn to/in each/dt lever/nn ./.
If/cs the/at lever/nn is/bez pulled/vbn to/to clear/vb a/at signal/nn or/cc move/vb a/at switch/nn ,/, the/at tappet/nn moves/vbz a/at short/jj distance/nn lengthwise/rb at/in the/at same/ap time/nn ./.


	Close/ql behind/in the/at plane/nn of/in the/at tappets/nns are/ber the/at locking/vbg bars/nns ./.
These/dts can/md also/rb move/vb a/at short/jj distance/nn but/cc at/in right/jj angles/nns to/in the/at tappets/nns ./.
The/at number/nn of/in locking/vbg bars/nns required/vbn depends/vbz on/in how/wrb many/ap false/jj moves/nns must/md be/be prevented/vbn ./.


	In/in the/at sides/nns of/in the/at tappets/nns are/ber notches/nns with/in sloping/vbg sides/nns ,/, and/cc connection/nn between/in the/at tappets/nns and/cc locking/vbg bars/nns consist/vb of/in cams/nns called/vbn ``/`` dogs/nns ''/'' ./.
Two/cd or/cc more/ap dogs/nns are/ber mounted/vbn on/in each/dt locking/vbg bar/nn ./.
These/dts slide/vb into/in and/cc out/in of/in the/at notches/nns in/in the/at tappets/nns as/cs the/at tappets/nns are/ber moved/vbn ,/, locking/vbg and/cc unlocking/vbg them/ppo ./.


	Here's/rb+bez how/wrb the/at scheme/nn works/vbz :/: Suppose/vb the/at operator/nn pulls/vbz the/at lever/nn to/to clear/vb a/at particular/jj signal/nn ./.
This/dt also/rb pulls/vbz the/at tappet/nn connected/vbn to/in the/at particular/jj lever/nn and/cc forces/vbz any/dti dogs/nns seated/vbn in/in the/at notches/nns to/in the/at side/nn ,/, thus/rb moving/vbg one/cd or/cc more/ap locking/vbg bars/nns ./.
The/at dogs/nns on/in the/at other/ap ends/nns of/in these/dts locking/vbg bars/nns are/ber thus/rb forced/vbn into/in notches/nns in/in other/ap tappets/nns ./.
By/in this/dt scheme/nn ,/, pulling/vbg one/cd signal/nn to/to clear/vb locks/nns all/abn the/at other/ap switch/nn and/cc signal/nn levers/nns in/in safe/jj positions/nns until/cs the/at first/od signal/nn is/bez again/rb restored/vbn to/in normal/jj ./.


	Interlocking/vbg signals/nns are/ber normally/rb at/in stop/nn or/cc ``/`` red/jj ''/'' position/nn ,/, and/cc a/at lever/nn must/md be/be pulled/vbn to/to ``/`` clear/vb ''/'' the/at signal/nn ./.
This/dt is/bez not/* necessarily/rb to/in green/nn ,/, however/wrb ,/, for/in in/in some/dti situations/nns only/rb a/at yellow/jj indication/nn is/bez given/vbn to/in a/at train/nn to/to let/vb it/ppo into/in the/at ``/`` plant/nn ''/'' ./.


	There/ex are/ber other/ap basic/jj rules/nns ./.
A/at turnout/nn may/md have/hv two/cd levers/nns ,/, one/cd to/to actually/rb move/vb the/at switch/nn points/nns ,/, the/at other/ap to/in lock/nn the/at points/nns ./.
A/at signal/nn cannot/md* be/be cleared/vbn until/cs all/abn the/at related/vbn turnouts/nns are/ber properly/rb thrown/vbn and/cc locked/vbn ./.
Such/jj locks/nns are/ber nearly/ql always/rb used/vbn where/wrb the/at switch/nn points/nns ``/`` face/vb ''/'' oncoming/jj traffic/nn ./.
The/at lock/nn insures/vbz that/cs the/at points/nns are/ber thrown/vbn all/abn the/at way/nn with/in no/at chance/nn that/cs a/at wheel/nn flange/nn will/md snag/vb on/in a/at partly/ql thrown/vbn point/nn ./.
If/cs the/at points/nns aren't/ber* thrown/vbn all/abn the/at way/nn ,/, the/at Turnout/nn-tl cannot/md* be/be locked/vbn ,/, and/cc in/in turn/nn ,/, the/at signal/nn cannot/md* be/be cleared/vbn ./.
Generally/rb ,/, these/dts locks/nns on/in turnouts/nns are/ber called/vbn ``/`` facing/vbg point/nn locks/nns ''/'' ./.


	Figs./nns 1-6/cd show/vb typical/jj arrangements/nns of/in track/nn and/cc signals/nns ./.
Each/dt diagram/nn is/bez accompanied/vbn by/in a/at ``/`` dog/nn chart/nn ''/'' ,/, a/at list/nn of/in the/at levers/nns that/wps show/vb which/wdt other/ap levers/nns any/dti particular/jj lever/nn will/md lock/vb if/cs pulled/vbn ./.
The/at lines/nns connecting/vbg the/at wedge-shaped/jj dogs/nns represent/vb the/at locking/vbg bars/nns at/in right/jj angles/nns to/in the/at tappet/nn bars/nns ./.


	By/in studying/vbg the/at track-signal/nn diagrams/nns you'll/ppss+md note/vb several/ap other/ap details/nns ./.
Derails/nns --/-- mechanical/jj track/nn devices/nns that/wps actually/rb guide/vb the/at wheels/nns off/in the/at rails/nns if/cs a/at train/nn passes/vbz a/at ``/`` stop/nn ''/'' signal/nn --/-- are/ber used/vbn in/in many/ap instances/nns ./.
``/`` Home/nr ''/'' signals/nns have/hv two/cd blades/nns ./.
The/at blacked-in/jj blades/nns indicate/vb a/at fixed/vbn aspect/nn --/-- the/at blade/nn does/doz not/* move/vb ./.
As/cs an/at engineer/nn approaches/vbz the/at plant/nn the/at position/nn of/in the/at home/nr signal/nn is/bez seen/vbn in/in advance/nn when/wrb he/pps passes/vbz the/at ``/`` distant/jj ''/'' signal/nn located/vbn beyond/in the/at limits/nns of/in the/at interlocking/vbg plant/nn ./.
In/in some/dti low-speed/nn situations/nns ,/, the/at distant/jj signal/nn is/bez fixed/vbn at/in caution/nn ./.
In/in other/ap instances/nns where/wrb there/ex is/bez no/at automatic/jj block/nn signaling/nn ,/, the/at distant/jj has/hvz only/rb green/jj and/cc yellow/jj aspects/nns ./.


	So/ql much/ap for/in the/at prototype/nn ./.


	The/at interlocking/vbg frame/nn we/ppss built/vbd at/in the/at model/nn railroader/nn workshop/nn and/cc then/rb installed/vbd on/in Paul/np Larson's/np$ railroad/nn follows/vbz the/at Fig./nn-tl 1/cd-tl scheme/nn and/cc is/bez shown/vbn beginning/vbg in/in Fig./nn-tl 7/cd-tl ,/, page/nn 65/cd ,/, and/cc in/in the/at photos/nns ./.
Here's/rb+bez how/wrb it/pps can/md be/be built/vbn ./.



Frame/nn-hl 
The/at sizes/nns of/in pieces/nns needed/vbn for/in the/at interlocking/vbg frame/nn are/ber shown/vbn in/in the/at notes/nns within/in Fig./nn-tl 7/cd-tl ,/, most/ap of/in the/at bars/nns being/beg 1/8''/nn ''/'' brass/nn in/in 1/4''/nn ''/'' and/cc 1/2''/nn ''/'' widths/nns ./.
You/ppss may/md change/vb the/at dimensions/nns to/to suit/vb a/at frame/nn for/in more/ap or/cc fewer/ap levers/nns and/cc locks/nns as/cs you/ppss wish/vb ./.
Our/pp$ instructions/nns assume/vb you/ppss are/ber building/vbg this/dt particular/jj frame/nn ,/, which/wdt is/bez for/in a/at junction/nn ./.


	When/wrb cutting/vbg the/at pieces/nns ,/, dress/vb the/at ends/nns smooth/jj ,/, and/cc square/vb with/in a/at smooth/jj file/nn or/cc sanding/vbg disk/nn ./.
Start/vb with/in the/at right-hand/nn piece/nn ``/`` B/nn ''/'' ,/, Af/nn ,/, soldering/vbg it/ppo to/in the/at lower/jjr piece/nn ``/`` A/nn ''/'' of/in the/at same/ap material/nn but/cc 12''/nns ''/'' long/jj ./.
Let/vb exactly/rb 1''/nn ''/'' of/in ``/`` A/nn ''/'' extend/vb beyond/in ``/`` B/nn ''/'' and/cc use/vb a/at square/nn to/to check/vb your/pp$ angle/nn to/in exactly/rb 90/cd degrees/nns ./.


	Now/rb lay/vb 12/cd pieces/nns of/in Af/nn cut/vbn 5-3/4''/nns ''/'' long/jj side/nn by/in side/nn but/cc separated/vbn by/in 12/cd pieces/nns of/in the/at same/ap material/nn 1/2''/nn ''/'' sq./jj ./.
This/dt gives/vbz you/ppo the/at spacing/nn for/in locating/vbg the/at left-hand/nn piece/nn ``/`` B/nn ''/'' ./.
Compress/vb the/at assembly/nn when/wrb you/ppss make/vb the/at mark/nn to/to show/vb the/at location/nn for/in ``/`` B/nn ''/'' ./.
Solder/vb this/dt second/od ``/`` B/nn ''/'' to/in ``/`` A/nn ''/'' at/in right/jj angles/nns ./.
There/ex should/md be/be 10''/nns ''/'' between/in the/at two/cd parallel/jj members/nns and/cc each/dt should/md be/be 1''/nn ''/'' from/in an/at end/nn of/in the/at long/jj piece/nn ./.


	Cap/vb this/dt assembly/nn (/( with/in spacing/vbg bars/nns in/in place/nn )/) with/in a/at Af/nn bar/nn ./.
Tack-solder/vb all/abn the/at 1/2''/nn ''/'' sq./jj pieces/nns to/in the/at 10''/nn ''/'' and/cc 12''/nn ''/'' members/nns ./.
These/dts will/md be/be drilled/vbn and/cc tapped/vbn later/rbr on/rp ./.


	Now/rb cut/vb five/cd Af/nn locking/vbg bar/nn spacers/nns (/( which/wdt run/vb horizontally/rb )/) ./.
Position/vb these/dts using/vbg six/cd intermediate/jj temporary/jj Af/nn spacers/nns and/cc locate/vb the/at upper/jj 12''/nn ''/'' bar/nn ``/`` A/nn ''/'' ./.
Solder/vb it/ppo and/cc the/at five/cd locking/vbg bar/nn spacers/nns to/in the/at frame/nn ./.
Now/rb place/vb 12/cd pieces/nns 1/2''/nn ''/'' sq./jj on/in this/dt edge/nn as/cs we/ppss did/dod before/rb and/cc space/vb them/ppo with/in the/at 5-3/4''/nns ''/'' long/jj ``/`` tappets/nns ''/'' ,/, as/cs they/ppss are/ber called/vbn ./.
Cap/vb with/in a/at Af/nn bar/nn and/cc tack-solder/vb in/in place/nn ./.
Cap/vb the/at locking/vbg bar/nn spacers/nns with/in two/cd Af/nn directly/rb under/in the/at first/od two/cd ``/`` B/nn ''/'' pieces/nns ./.
Remove/vb all/abn the/at loose/jj spacing/vbg bars/nns ./.


	Mark/vb and/cc center-punch/vb all/abn the/at holes/nns required/vbn for/in screws/nns to/to hold/vb this/dt assembly/nn together/rb ./.
See/vb Fig./nn-tl 7/cd-tl ./.
Placement/nn of/in these/dts holes/nns is/bez not/* critical/jj ,/, but/cc they/ppss should/md be/be located/vbn so/cs that/cs the/at centers/nns are/ber about/rb 1/8''/nn ''/'' from/in any/dti edge/nn ./.
Drill/vb all/abn No./nn-tl 50/cd-tl and/cc counter-drill/vb all/abn except/in the/at ``/`` A/nn ''/'' pieces/nns size/nn 43/cd ./.
Tap/vb the/at ``/`` A/nn ''/'' pieces/nns 2-56/cd ./.


	Now/rb unsolder/vb and/cc disassemble/vb the/at frame/nn except/in for/in the/at two/cd 12''/nn ''/'' and/cc the/at first/od two/cd 3-3/4''/nns ''/'' bars/nns (/( ``/`` A/nn ''/'' and/cc ``/`` B/nn ''/'' pieces/nns )/) ,/, which/wdt are/ber soldered/vbn together/rb ./.
Either/cc lay/vb the/at components/nns aside/rb in/in proper/jj order/nn or/cc code/vb them/ppo with/in numbers/nns and/cc letters/nns so/cs they/ppss may/md be/be replaced/vbn in/in their/pp$ proper/jj positions/nns ./.
Dress/vb all/abn surfaces/nns with/in a/at file/nn ,/, cleaning/vbg off/rp all/abn solder/nn and/cc drilling/vbg burrs/nns ./.


	Drill/vb 20/cd No./nn-tl 47/cd-tl holes/nns in/in the/at upper/jj piece/nn ``/`` A/nn ''/'' as/cs shown/vbn in/in Fig./nn-tl 7/cd-tl ./.
Tap/vb these/dts 3-48/cd for/in mounting/vbg the/at electrical/jj contact/nn later/rbr on/rp ./.
Note/vb ,/, 6/cd and/cc 8/cd lock/nn levers/nns don't/do* require/vb holes/nns for/in contacts/nns ./.


	Now/rb reassemble/vb the/at frame/nn ,/, using/vbg Af/nn roundhead/nn steel/nn screws/nns and/cc nuts/nns ./.
Put/vb the/at 12/cd tappets/nns and/cc some/dti Af/nn locking/vbg bar/nn spacers/nns in/in the/at frame/nn to/to help/vb align/vb all/abn the/at components/nns before/cs you/ppss tighten/vb the/at screws/nns ./.
Be/be sure/jj the/at tappets/nns are/ber not/* pinched/vbn by/in a/at twisted/vbn 1/2''/nn ''/'' sq./jj spacer/nn ./.
As/cs an/at anchor/nn for/in the/at spring/nn lock/nn ,/, insert/vb a/at Af/nn bar/nn in/in the/at lower/jjr left/jj corner/nn of/in the/at frame/nn as/cs shown/vbn in/in Fig./nn-tl 7/cd-tl ./.
Drill/vb a/at No./nn-tl 43/cd-tl hole/nn through/in the/at pieces/nns and/cc secure/vb with/in a/at 2-56/cd nut/nn and/cc screw/nn ./.
Drill/vb two/cd No./nn-tl 50/cd-tl holes/nns ,/, one/cd in/in the/at insert/nn and/cc one/cd in/in the/at locking/vbg bar/nn spacer/nn directly/rb above/in it/ppo ,/, and/cc tap/vb 2-56/cd ./.
Number/vb all/abn the/at tappet/nn bars/nns before/cs removing/vbg them/ppo so/cs they/ppss can/md be/be replaced/vbn in/in the/at same/ap slots/nns ./.
Remove/vb all/abn other/ap loose/jj pieces/nns and/cc file/vb the/at edges/nns of/in the/at basic/jj frame/nn smooth/jj ./.
Cut/vb five/cd pieces/nns of/in Af/nn brass/nn bar/nn stock/nn 3-3/4''/nns ''/'' long/jj ./.
These/dts are/ber supporting/vbg members/nns for/in the/at short/jj locking/vbg bars/nns ./.
Locate/vb their/pp$ positions/nns in/in Fig./nn-tl 7/cd-tl and/cc drill/vb No./nn-tl 43/cd-tl to/to match/vb the/at corresponding/jj holes/nns in/in the/at frame/nn ./.
Cut/vb off/rp excess/jj screw/nn lengths/nns and/cc file/vb flush/jj with/in either/cc frame/nn or/cc nut/nn ./.
Drill/vb four/cd No./nn-tl 19/cd-tl and/cc four/cd No./nn-tl 28/cd-tl holes/nns in/in the/at 12''/nns ''/'' long/jj ``/`` A/nn ''/'' pieces/nns ./.
Locate/vb the/at position/nn from/in Fig./nn-tl 7/cd-tl ./.



Tappets/nns-hl and/cc-hl locking/vbg-hl bars/nns-hl 
Draw-file/vb No./nn-tl 1/cd-tl tappet/nn to/in a/at smooth/jj fit/nn in/in its/pp$ respective/jj slot/nn and/cc square/vb the/at ends/nns ./.
Break/vb the/at end/nn corners/nns with/in a/at slight/jj 45/cd degree/nn chamfer/nn ./.
Drill/vb a/at No./nn-tl 50/cd-tl hole/nn 1-1/4''/nn ''/'' from/in one/cd end/nn and/cc tap/vb 2-56/cd ./.
(/( See/vb Fig./nn-tl 7/cd-tl ./.
)/) Put/vb a/at 2-56/cd roundhead/nn screw/nn into/in the/at hole/nn ,/, cut/vb off/rp the/at excess/jj threads/nns and/cc file/vb flush/jj with/in the/at underside/nn of/in the/at bar/nn ./.
To/to find/vb the/at other/ap stop/nn screw/nn position/nn ,/, insert/vb the/at tappet/nn into/in the/at frame/nn and/cc hold/vb the/at screw/nn head/nn tight/rb against/in the/at frame/nn edge/nn ./.
Scribe/vb a/at line/nn across/in the/at bar/nn on/in the/at other/ap end/nn of/in the/at tappet/nn ,/, 1/4''/nn ''/'' plus/cc half/abn the/at diameter/nn of/in the/at 2-56/cd screw/nn head/nn (/( about/rb 5/64''/nn ''/'' )/) away/rb from/in the/at frame/nn edge/nn ./.
Total/nn distance/nn is/bez about/rb 21/64''/nns ''/'' ./.
Tend/vb to/to make/vb this/dt dimension/nn slightly/ql undersize/jj so/cs you/ppss can/md file/vb the/at screw/nn head/nn to/to get/vb exactly/rb 1/4''/nn ''/'' tappet/nn movement/nn ./.
Drill/vb a/at No./nn-tl 50/cd-tl hole/nn ,/, tap/vb 2-56/cd and/cc insert/vb a/at roundhead/nn 2-56/cd screw/nn as/cs you/ppss did/dod on/in the/at first/od end/nn ./.
Drill/vb a/at No./nn-tl 47/cd-tl hole/nn crosswise/rb through/in the/at tappet/nn at/in the/at position/nn shown/vbn in/in Figs./nns-tl 7/cd-tl and/cc 8/cd-tl ./.
Repeat/vb these/dts drill/vb and/cc tap/vb operations/nns for/in each/dt of/in the/at tappet/nn bars/nns ./.


	To/in each/dt tappet/nn except/in 6/cd and/cc 8/cd ,/, solder/vb a/at Af/nn piece/nn of/in brass/nn and/cc file/vb to/in the/at tapered/vbn shape/nn shown/vbn in/in Figs./nns-tl 6/cd-tl and/cc 8/cd-tl ./.
These/dts will/md serve/vb as/cs lifting/vbg pads/nns for/in the/at electrical/jj contacts/nns ./.


	Fitting/vbg the/at locking/vbg bars/nns and/cc making/vbg the/at locking/vbg pieces/nns is/bez a/at rather/ql tedious/jj job/nn since/cs stop/nn screws/nns ,/, tappets/nns and/cc locking/vbg bars/nns must/md be/be removed/vbn and/cc replaced/vbn many/ap times/nns ./.
As/cs the/at work/nn progresses/vbz the/at frame/nn and/cc moving/vbg parts/nns become/vb a/at sort/nn of/in Chinese/jj puzzle/nn where/wrb several/ap pieces/nns must/md be/be removed/vbn before/cs the/at part/nn you/ppss are/ber working/vbg on/in is/bez accessible/jj ./.
A/at little/ap extra/jj work/nn here/rb will/md pay/vb off/rp with/in a/at smooth/jj ,/, snug-fitting/jj machine/nn when/wrb you/ppss are/ber finished/vbn ./.
Each/dt completed/vbn locking/vbg bar/nn should/md remain/vb in/in place/nn as/cs the/at work/nn progresses/vbz to/to insure/vb snug/jj fitting/nn ./.


	The/at order/nn of/in fitting/vbg is/bez not/* too/ql important/jj ./.
However/rb ,/, we/ppss started/vbd with/in the/at first/od row/nn of/in bars/nns and/cc worked/vbd our/pp$ way/nn back/rb ./.
Since/cs the/at same/ap method/nn of/in shaping/vbg and/cc fitting/vbg the/at dogs/nns and/cc notches/nns is/bez used/vbn throughout/rb ,/, we/ppss will/md only/rb describe/vb the/at construction/nn of/in one/cd locking/vbg bar/nn ./.
Figs./nns-tl 7/cd-tl and/cc 8/cd-tl give/vb all/abn pertinent/jj dimensions/nns ./.
All/abn the/at bars/nns are/ber cut/vbn from/in Af/nn brass/nn ./.
The/at lengths/nns of/in each/dt piece/nn are/ber listed/vbn at/in the/at bottom/nn of/in Fig./nn-tl 7/cd-tl ./.
Bar/nn ``/`` C/nn ''/'' is/bez 2-3/4''/nns ''/'' long/jj ./.
Draw-file/vb the/at edges/nns ,/, square/vb up/rp the/at ends/nns and/cc put/vb a/at slight/jj chamfer/nn on/in the/at edges/nns so/cs they/ppss will/md not/* snag/vb in/in the/at frame/nn ./.


	Fig./nn-tl 8/cd-tl gives/vbz the/at dimensions/nns for/in locating/vbg the/at dog-pin/nn holes/nns ./.
Center-punch/vb and/cc drill/vb the/at No./nn-tl 31/cd-tl hole/nn 7/16''/nn ''/'' from/in one/cd end/nn of/in the/at bar/nn ./.
Chuck/vb a/at length/nn of/in 1/8''/nn ''/'' dia./nn drill/nn rod/nn into/in a/at drill/nn press/nn or/cc some/dti similar/jj turning/vbg device/nn and/cc while/cs it/pps is/bez rotating/vbg file/vb the/at end/nn square/jj and/cc then/rb file/vb a/at slight/jj taper/nn 1/8''/nn ''/'' long/jj ./.
Cut/vb the/at piece/nn about/rb 9/32''/nn ''/'' or/cc 5/16''/nn ''/'' long/jj and/cc drive/vb it/ppo into/in the/at No./nn-tl 31/cd-tl hole/nn drilled/vbn in/in the/at locking/vbg bar/nn ./.
File/vb the/at bottom/nn edge/nn flush/jj with/in the/at bar/nn and/cc the/at top/nn 1/8''/nn ''/'' above/in the/at bar/nn ./.
This/dt dog/nn will/md engage/vb a/at notch/nn to/to be/be cut/vbn in/in tappet/nn 3/cd ./.


	Place/vb the/at locking/vbg bar/nn in/in proper/jj position/nn and/cc insert/vb tappet/nn 3/cd ./.
Scribe/vb a/at line/nn through/in the/at center/nn of/in the/at pin/nn and/cc across/in the/at face/nn of/in tappet/nn 3/cd ,/, parallel/jj to/in piece/nn ``/`` A/nn ''/'' ./.
See/vb the/at drawings/nns for/in the/at shape/nn of/in the/at notch/nn ./.
Scribe/vb V-shaped/nn lines/nns on/in the/at bar/nn and/cc rough/vb out/rp with/in either/cc a/at hack/nn saw/nn or/cc a/at cutting/vbg disk/nn in/in a/at hand/nn power/nn tool/nn ./.
We/ppss used/vbd the/at latter/ap equipped/vbn with/in a/at carborundum/nn disk/nn about/rb 


''/'' thick/jj and/cc 1''/nn ''/'' dia./nn fitted/vbn on/in a/at 1/8''/nn ''/'' dia./nn mandrel/nn ./.
Such/jj disks/nns are/ber very/ql handy/jj for/in cutting/vbg and/cc shaping/vbg small/jj parts/nns ./.
File/vb to/in a/at smooth/jj finish/nn ./.
A/at Barrette/np Swiss/jj pattern/nn file/nn is/bez handy/jj since/cs its/pp$ triangular/jj shape/nn with/in only/ap one/cd cutting/vbg face/nn will/md allow/vb you/ppo to/to work/vb a/at surface/nn without/in marring/vbg an/at adjoining/vbg one/cd ./.
Endeavor/vb to/to get/vb the/at notches/nns as/ql much/ql alike/jj as/cs possible/jj ./.
The/at notch/nn should/md have/hv a/at smooth/jj finish/nn so/cs that/cs the/at steel/nn dog/nn will/md slide/vb easily/rb over/in it/ppo ./.
Assemble/vb the/at parts/nns in/in the/at frame/nn and/cc test/vb the/at sliding/vbg action/nn of/in the/at mating/vbg pieces/nns ./.
All/abn matching/vbg surfaces/nns should/md be/be checked/vbn frequently/rb and/cc mated/vbn on/in a/at cut/vb and/cc fit/vb basis/nn ./.


	Chuck/vb a/at 2''/nn ''/'' or/cc 3''/nn ''/'' piece/nn of/in 1/8''/nn ''/'' dia./nn drill/nn rod/nn in/in a/at drill/nn press/nn or/cc electric/jj hand/nn tool/nn ./.
Fashion/vb a/at sharp/jj scribing/vbg point/nn about/rb 3/64''/nn ''/'' long/jj on/in one/cd end/nn ,/, using/vbg Swiss/jj pattern/nn files/nns ./.
This/dt tool/nn can/md also/rb be/be made/vbn with/in a/at lathe/nn ./.

