The Starrett PT99002 Lock Bolt Assembly is a combination square head tool designed for precise measurements in metalworking inspection and measurement tasks. Made of steel and manufactured in the United States, this product is compatible with #11-12", 18", and 24" square heads, providing a reliable and accurate solution for professionals in CNC, metalworking, and manufacturing industries. With the Starrett brand known for quality and durability, this lock bolt assembly is a trusted tool for achieving precise measurements in various industrial applications.