Knowing that rats are chewers, you'd be surprised just how many of the bottoms or sides of rat cages are made out of plastic, a substance that rats can chew through very easily. This is a picture of the holding cage I had Lucky in when he was 4 months old. He was small and so he was the perfect size for this cage while I waited for the bigger cage to arrive in the mail. But before I bought the other cage, Lucky decided to chew his way out. lol He chewed that hole in the plastic bottom of the cage, so I changed the other cage I was going to get, for a metal chew proof bottom cage.
This was the cage Lucky chewed his way almost out of. He was a tiny little thing when I first adopted him so this was perfect for him until he grew a bit and I didn't have to worry about him slipping through the bars of the cage.
This is the metal bottom cage that I bought for my little chewer. 3 levels and plenty of room for him to run around and best of all, he couldn't chew the bottom.
Now that Bandit *bottom* has passed away a few month ago and Marbles *top* is older and not getting around very well. Marbles is in a single level cage like the one Lucky chewed his way through and Lucky is in this big cage and my smaller Scribbles is in his older 3 level cage.
I switch the rats around different cages as their needs get different. The bottom that is covered in a fleece blanket in this larger cage is also plastic but thankfully now that Lucky is older, he doesn't chew as much as he used to. But if I had to I could buy a metal replacement bottom for this cage. I actually like metal bottoms better because I don't have to worry about them breaking, being chewed on and metal is easier to clean than the plastic is. Plastic seems to keep some of the smell where metal doesn't.