The protractor head on a combination square is used to _____.

The protractor head on a combination square serves the specific purpose of laying out various angles. It features a calibrated arc with degree markings that allow users to accurately measure and set angles between two surfaces or lines. This function is essential in many tasks, such as carpentry, metalworking, and machining, where precise angle measurements are critical for the accuracy of cuts and connections.

By utilizing the protractor head, a user can easily determine and mark desired angles, thus ensuring precise angles in construction and manufacturing projects. The design and scale of the protractor head enhance the ability to work with both common and unique angles required in various applications.