Flannel is generally made with either a twill or percale weave. The fabric is then napped to hide the weave. Napping is a finishing technique that gives flannel that signature fluffy, fuzzy feel. Flannel can be napped on just one side, or it can be double-napped, meaning both sides of the fabric are napped, for extra softness. Flannel is also often sheared after napping for a smoother texture.