 This creates the back of the channel and is the basis for the letter shape.The sides of the channel letter, called the "returns", are then formed by bending a strip of aluminum sheet around the aluminum back.This return can be welded at the seam or flanged and riveted or, with a metal stitcher, can be fastened with galvanized or stainless wire to the back to create a solid "can" in the shape of the letter.