It is a metal piece, whose function is to join two or more elements, this type of bolt has a hexagonal head, made of carbon steel, quenched and tempered, high resistance for use in the mechanical and automotive industry, its resistance of load is similar to those of the grade 5 screw, it is identified by the number that it has in the upper part of the hexagon. The finish of the screws is black with different thread pitches, bearing in mind that by mentioning a 961 screw we mean that it is fully threaded.