I keep them all, the bigger pieces I join with others. I have a really large bag of little pieces I intend to use for a dog bed. I have saved some of them and stuffed a muslin bag I made to put in a pillow case. I generally just lay them over lapping the edge and cut with my rotary cutter and whip stitch them together. I have used the zig zag on my machine and I have made my own joining tape using the lightest weight fusable interfacing, that was before they came out with the tape made for the purpose of joining the batting. I hate to cut a large piece of batting for a small project, I've been know to join three or four small pieces together. I always keep the different batting together and don't use all cotton with a poly blend.