Time: ~half hour
-old cantilever brake bars
-filing device(s) (I used both a hand file and a wheel grinder)
-drill: if your brake holes aren't already big enough
Step 1: Select the "right" arm
Select the "right" arm (see picture)
Step 2: Cut
Cut off the extra, third arm. You should be left with a curved "L" shape. The top of the L (where the metal is twisted perpendicular to the rest of the piece, with the larger hole) will attach to the bike frame. The OTHER end inserts into the bike trailer.
Step 3: File
File the arm that inserts into the bike trailer only as much as needed to get it to slide in. File as even of a surface as you can.
Step 4: Attach Axle Mount
Attach axle mount to your bike.
If you have a bolt style rear axle, you may need to attach the axle mount to the holes in the frame for a bike rack.
If the axle mount hole IS big enough to fit around your rear axle, remove the left lugnut (side w/o the gears) slip it on, and re-tighten the lugnut. Extra washers here might be a bonus.
Step 5: Hitch and go!
You're done. Now get out of here!
Happy peddaling :-)