i used a plastic grate material that i got from a craft store to enclose the back of my canopy. the material is used for cross stiching with yarn, it's a common sort of a kiddie craft thing. it's easy to use because it cuts with scissors, and the grid pattern makes it easy to measure, and cut straigh lines. the holes are only about 1/8 of an inch. i just attached it to the back of the canopy with thumb tacks so i can remove it easily. haven't had an escape since.