Thrumming is an easy technique where bits of unspun fleece are worked into the knitting, creating a design element on the right side and a soft, fleece lining on the inside. The hardest part is finding the fleece. Raven Frog Thrum kits come in all the Raven Frog colorways and include 4 oz. variegated merino yarn and the fleece in a coordinating solid. Instructions for how to work a thrum stitch are included in the pattern.