The boxes are simple, fast and cheap to build. They are just a three sided box hinged off a wooden block attached to the bottom. I used scraps of cedar fence board for the sides and 2” thick cedar blocks for the hinge. The sides are screwed into the block and I used a washer on these screws to reduce wear and tear. The two parts pivot on the screws. I drove a staple in the to of the hinge block to wire bait off to.
The width of the boxes are good but the interior at 5 1/2” is too tall. The back frame of these little rat traps is only 4”. I think this gap encourages critters to come in head high trying to go over rather than through the trap. This causes the strike bar to push the animal clear when the trap is fired.
You could rip down the sides to 4 1/2” to save weight and space but I will just use some filler under or above the trap. My reason for this is that I like the volume of the box as I can fit a whole duck carcass behind the trap.
These won’t nest while assembled but it would be easy to take the bottoms off for transportation and then reassemble them in the field. It would just take two screws or a single through bolt.