>>...thought about making a cage out of those 'heavy duty storage racks' that they sell at homedepot? The kind with slotted 90 degree posts, and particle board levels?
Personally I would advise against it. I've used those types of shelving before simply as shelving and been thoroughly dissatisfied. The weakness is in the 90 degree slotted sections. If they even get slightly bent it causes the entire shelving unit to buckle. Also, I stored a reptile cage on one once and the cage was not one of my better ones and it leaked water. The leakage out of the cage caused the particle board to swell and buckle and eventually begin to crumble. There are so many obstacle to overcome to make something like this into a halfway decent cage you'd be better off starting from scratch with other building materials. Starting from scratch you'll make no compromises in your design. Believe me, I'm one of the kings of making cages from other things that didn't start life as a cage. I've never been satisfied with any cage I made by converting something else because there have always been far too many compromises to make a non-cage item into a cage.
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Matt Campbell
"I only went out for a walk and finally concluded to stay out till sundown, for going out, I found, was really going in." John Muir