A clip has a base A having a U shape composed of a pair of parallel sections, and a joining section having flexibility and interconnecting the lower parts thereof, elastic pieces respectively branching from the insides of the parallel sections in the opposed directions, and extending along the parallel sections and the joining section, claws respectively protruding inwardly on the elastic pieces, and step sections having upper surfaces respectively projecting outward from the outer sides of the parallel sections and being inclined obliquely downward.