The fixed rivets make the connection firmer, safer, and more durable. The fine adjustment screw is easy to adjust to the appropriate size for tightening, and the round saw teeth are strong for holding things. The labor-saving connecting rod is made of high-carbon steel, and the mechanical connecting rod is used to connect the two handles to achieve the effect of tightening and labor-saving. The caliper body is forged from high-carbon steel, which is heat-treated, with high hardness and long service life.