You might want to build just a screen piece to go over it. If you use just the plastic lattice they will just go through the holes to let themselves in. And you may think that the holes are too small - but they aren't. I had a Maine Coon who weighted 27lbs. And she was able to squeeze herself between the box spring and the bed frame which had a gap of only 1 1/2 inches. It is amazing how they can make themselves fit.