Hi, /out/: In Wilderness and National Park areas I go to in Montana and Wyoming, they have signs that food must be stored in a vehicle or "approved" bear-proof container.

I ask because I would like to make a box for my cooler and other supplies in the front of my trailer (used for hauling ATVs).

Would plywood be enough, with tough latches and hinges? I can weld together steel, but rust is so ugly without a factory finish of powder coating or something. Aluminum would be another choice, but expensive, and could a bear just rip through it?

TLDR; anybody know what makes an "approved" bear-resistant box?