What is the removable blade of a combination square used for?

The removable blade of a combination square primarily serves the purpose of making layout lines at 45° and 90° across the face or edge of stock, which is indeed a crucial function in carpentry and building construction. This blade can be adjusted and set at precise angles, allowing the carpenter to create accurate markings for cuts, ensuring that materials are shaped and aligned correctly according to design specifications.

While checking adjacent surfaces for the correct angle is part of what a combination square can do, the specific function of the removable blade focuses on making layout lines, which is essential for ensuring that the workpiece is cut and joined accurately. Similarly, leveling or plumbing surfaces is a different function that involves the spirit level component of the square and not the removable blade itself. The distinct capability of the blade emphasizes its role in precision work, which is foundational in the carpentry field.