Pegboard holds up surprisingly in herp applications. I have some cage tops that are pegboard and have stood the test of time.
Cutting pegboard is easy with a circular saw or tablesaw, but man oh man is the sawdust aweful. Wear a mask - that stuff is very fine and gets on you and in your eyes and nose - and it is a health hazard to breathe in apparently.
You can make a rack with it as the bottom and top of the plastic box, but you must build a frame under each pegboard shelf - it won't hold a box well enough without some kind of framing under it.
Someone posted a pic in one of the forums showing a pegboard rack for adults. I'll try to describe it below:
Cut shelves from pegboard sized to the box you intend to use with adequate overlay around the box top. You will need to glue or screw wood pieces around the perimeter of the shelf (non-vinyl side) and maybe two supports within the rectangle frame. Use wood glue if you use glue, as Liquid Nails smells forever it seems like.
I think that the 3/4" square pine molding is good for the frame on the shelves, but this gets pricey. Some people use 1x2 furring strips, but furring strips aren't straight. Some people use strips of plywood cut from one large piece. This is cost-effective and works very well. Plus, plywood doesn't change shape as much as pine. Extruded aluminum hollow square is the best (use rivets to attache shelf), but it costs so darn much.
The next shelf up will need pegboard attached to both sides of the frame (all shelves have the vinyl side touching the box bottom and top.) Continue with as many shelf modules as you need.
Once you have all of your shelf modules made, you'll need to make the rack frame to attach all of the shelf modules to, basically 2 sides and a back (or open back). The frame can be plywood or 2x4s or melamine. I think plywood sides are a great choice here.
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Mark