I did have one of those vinyl tunue cover things stretched over the aluminum things with the snaps...
Anywho, a coon ripped a big hole in it trying to get at some fish bait I forgot about in there. But, it worked out in the long run, 'cause when I got the tool box, I just cut that end off! I cut the rails down, and pulled the vinal up tight, turned it under, and secured it with some aluminum plates and pop rivets.
How-some-ever, we were lay'n in fire wood at her brother's house, (which she's house-sitting) the other day, and we took the cover off for bed access. Now I go to put it back on, and I found a big gash in it! WTF!