When I first put my 4 pound puppy in I thought wow, now I can get some rest and start training. The first nite she climbed out and I woke up to a mess. Her and her cat pal had a grand old time and she got into the rooms with cat boxes while her new pal Nicky, a cat we'd trapped, taught her the ropes. I call those two my little thugs. They pick on the old and sick critters and steal their toys and food. Then not wanting to be out-foxed by such a small creature I picked out a piece of vinyl from my sewing room, some grommets and zip ties and went to work. It worked and the pen works great. Now the rest of the critters are happier and I get a little rest from the 4 pound hoodlum. Nicky the cat is the only one hurting because he doesn't have his gang to run with and wreak havoc.