How high should the sides of a tortoise table be? I'm thinking 12" because then Walter can have 4 or 5 inches of digging fun... Does she actually need to dig? She seems to love it so I'd assume depth is an important factor in a table just for her...
My rule of thumb has always been to imagine a tortoise laying next to the wall, then another tortoise climbing on the first tortoise's back and reaching up to the top with his front legs. If he can reach to top, the sides are too short. And don't forget to take into consideration the substrate. The more substrate you have, the shorter the sides are.
That's good advice. And it is nice for them to be able to dig, makes it more interesting. The other option is to 'cap' the edges with a piece of trim (overhang) to be on the safe side.
This is a nice tort table because you can make the sides higher, yet it lets light in: http://www.tortoisetrust.org/articles/Tortoisetable.htm