1/4" is only a tiny setback for a rat to chew through. Don't bother, go straight for 1/2". You can cut the 1/4" with plain scissors, rats would find it no problem to get through.

Holes can start getting chewed as well, but that's up to each individual rat. Some may, some may not. You DO need to give them optimum ventilation. Using 1/2" hardware cloth on the lid and top part of the tub is the best way to do it.

Check out FrankyKeno's rat tub DIY post. It is an excellent write up.
http://www.ball-pythons.net/forums/s...ad.php?t=56321