Device for applying a protective material on one edge of a part, includes a body equipped with elements for applying the protective material on the edge, elements for calibrating the protective material in terms of height after application, at least one stop to position the body relative to the edge and elements for calibrating the edges of the protective material including two smoothing plates that rest respectively against the right and the left surfaces of the part adjacent to the edge, at least one of the two smoothing plates being movable relative to the other smoothing plate. The body includes at least one arm that supports a smoothing plate and pivots relative to the body around an axis of rotation so as to regulate the spacing between the two smoothing plates and return elements that tend to make the arm pivot so as to bring the smoothing plates close together.