What is the primary function of a square head in a measuring tool?

The primary function of a square head in a measuring tool, particularly in the context of carpentry and construction, is to serve as a height gauge. This usage is primarily seen in tools like combination squares or framing squares where the square head allows for precise measurements of height and depth when checking aligns or marking straight lines. The flat edge of the square head can rest firmly on a surface, providing a straight reference point from which measurements can accurately be taken.

This functionality is critical when ensuring that materials are cut or installed to the correct specifications. It allows for consistency and accuracy in various applications, especially when working with materials that need to fit together perfectly at precise angles and heights.