I use Pellon 71F, a very heavy, fusible interfacing. I make a sleeve to match the lining of the purse/tote, then slip the Pellon in and fuse it well. This stuff is super heavy, works really well on the bags, but when I have a large tote, I ususally double it. I like having it match the purse, especially if it's for someone else, ergo the sleeve.