Crutch
From Wiki Weed
Usually made from a small piece of thick paper (such as the inner lining of a cigarette carton or the outer flap of a pack of rolling papers), a crutch is a short cylinder rolled into a joint or spliff at the side that touches your lips. The crutch serves a dual purpose: first, it prevents the end of the joint from getting wet and collapsing in on itself, making smoking it rather unpleasant. Second, it makes rolling the joint easier: the shape of the crutch determines, at least to a certain extent, the shape of the joint.