Well I did try that brick thing back when we had pet rats. It may well help keep their nails back a bit but it just gets nasty! We provide our colony with enough hard foods, bones, etc. that they can grasp and chew on and I think that it works just fine. We have retired breeders with us that are well on 2 years plus now and even they don't seem to have issues with overgrown of nails or teeth.