After a lot of rides where we would cram our 4yr olds bike into back pocket of our trailer, figured it would be great to have a little rack instead! This way it frees up pocket for other gear and also avoid pedals from poking your poor kids in the back!

I found these little 4" hooks at home depot worked perfect and costs less than $2 each. All parts included it was less than $8, and you could do it cheaper if you already had screws or didn't care about using stainless parts. I had some extra mini bungee cords lying which can help secure the bike, though not sure its really necessary. If you wanted to take it to the next level some little velcro straps might be nice addition!

Placement of hooks may vary slightly depending on your trailer, i found that in order to still be able to collapse our particular burley bee trailer i needed to angle the hooks inward slightly so they didn't run into opposing front bar section when folded flat. One other small note is when collapsing you'll just need to undo the velcro attachments on back pocket as they wont slide down the rail once hook is installed.

Supplies

(2) 4" hooks: https://www.homedepot.com/p/Everbilt-4-in-Handy-Ho...
(4) 1/4" x 1 3/4" screws: https://www.homedepot.com/p/Everbilt-1-4-in-20-x-1...
(4) 1/4" lock nuts: https://www.homedepot.com/p/Everbilt-1-4-in-20-tpi...

Step 1: Test Out Collapsability

This is really the only tricky part of the whole thing, to make sure you can still collapse the trailer if you want. I was able to tuck hooks under existing velcro straps snug enough to give a good idea how it would work when trailer is collapsed before drilling the holes. In my case i found i had to angle the hooks inward slightly to avoid colliding with front bar. I'm guessing most of the burley brand trailers would probably have same issue.

Step 2: Clamp It Up!

Clamps are a good idea here just to make sure you maintain the right inward angle of hook while drilling both holes. Use a 1/4" drill bit assuming you are going with 1/4" screws and nuts, slightly smaller screws would also work fine with the hook.

Step 3: Screw It Up!

for fellow building noobs like myself, you may not realize there is such thing as a lock nut which is slightly different from normal nut in that it has nylon threads to avoid coming loose with vibration which seemed like a good idea here!

Step 4: Tie It Down

Probably this isn't really necessary but some extra assurance the bike won't go flying off if you hit a monster pot hole is always nice. I had some mini bungee cords laying around so i just hooked that around, but a velcro strap or some other method could also be cool.