I have a very similar Jansport daypack. I use the loop to secure my cathole trowel to the outside of the bag.
If I wanted to roll something larger up and carry it, I would wrap a couple of small bungees around it and secure them to the plastic loop and the fabric handle loop.
BTW, I fit an arctic fleece blanket, a Clark Untralite Jungle hammock, titanium pot, 2 changes of clothes, a wind suit, poncho, Katadyn water filter, a 1 quart water bottle, a folding saw and everything needed for a 7-day trip in one of those plus a fanny pack (worn in front) which holds the most essential survival supplies.
I carry a minimum of food as I supplement it with foraging and fishing. I need to work on my trapping skills.
I had a full sized backpack, but couldn't resist carrying too much, which made the pack way too heavy for me to carry. So I switched to the day pack and fanny pack combination. It forces me to eliminate all the "just in case" items.
[This message has been edited by Tadpole (edited 05-24-2001).]