Metal object, on one end it is sharp and there is a head on the other, utilized to unite two elements of wood through a hammering impact. Nails come in various types and lengths according to their use. The forged nail presents a triangular or quadrangular section and, with respect to modern industrial production, it is easily recognizable for its irregularity on the surface of the leg. In paintings on wood panel, the presence of nails in the support produces localized tension and weakening that may provoke breaking in the wood.