I use batting tape I got from Nancy's Notion site but I'm sure other sites have it too. There are 2 widths so be careful which one you order. I got the wider one and use it all the time to piece my batting leftovers. Also make sure that the pieces are turned on the correct side before adding the tape. After I've added a piece, I pin a scrap paper with the size of the pieced batting so I know if it will work on my next project or if I need to add another piece to make it fit. This keeps the cutoffs at a minimum laying around. I keep the smaller pieces under my cutting table for when I'm making embroidered items that need a piece of batting. So not much goes to waste.