i save all of the pieces i cut off finished quilts and keep them, then when i have smaller (like kid's quilts) projects i get into my 'scrap-bag' and find pieces that are about the same weight (i use lots of different battings so always have choices to pick from) i put the pieces side by side edges butted up to each other and use a wide zigzag to stitch the pieces together until it is the right size for what i am working on. really small pieces i use in table runners, placemats, coasters ect. but if the piece is long and at least 6" wide i save it for pieced batts.