Source: Martha Stewart Living, December 2006
Give plain winter hats, mittens, and other items a decorative touch with a simple technique called needle felting. Letters and designs can be added to articles by using wool roving, a textile similar to unwoven yarn.
Medium-blade felting needle
Start with clean 100 percent woolen accessories. Place a clean sponge between layers in a hat or mittens, and secure a stencil on top with straight pins. Pull off a small clump of roving, and place it over stencil.
Using a medium-blade felting needle, pierce roving, and press the needle through article. Continue piercing roving until stencil is filled in. (The needle, which has small notches near the point, will interlock roving and wool.) When finished, hand-wash the item, and dry flat to secure the design.