I have tried various items. I went to a carpet place and thy sold me some scraps of linoleum, It was very very reasonable and I could cut to fit or even piece them together.. I have also used heavy vinyl table cloths or shower curtains. All 3 work good. I like the table cloths or even you could buy bulk vinyl from walmarts fabric section.I bought 5 yards of some thick plastic table covering that has a pattern printed in it and it was so cheap I could throw it away if there was a mess I didnt feel like cleaning .I just cut it a little bigger than the pen and if they move it a lot I clipped it with small clips at a few spots on the outside of the expen |