1/2-13 X 2 1/2 SQUARE BOLT A307 GRADE A

A square bolt is a type of bolt that has a square-shaped head instead of the more common hexagonal head. The square head allows for a wrench or a specialized square socket to be used to tighten or loosen the bolt.

Square bolts are often used in applications where it's necessary to prevent rotation during installation or removal. The square head design makes it less likely for the bolt to slip while being turned, providing better control over the torque applied.