What is a squaring tool with a graduated blade attached at a 90° angle to the handle?

A squaring tool with a graduated blade attached at a 90° angle to the handle is known as a try square. The design of a try square allows for precise measuring and marking of right angles, making it essential for ensuring accuracy in various carpentry and metalworking tasks. The graduated blade provides a way to make measurements, ensuring that components are cut or placed correctly.

In contrast, while the rafter angle is used for laying out roof rafters and checking angles, it does not have the same graduated scale or structure as a try square. The sliding T-bevel is primarily used for transferring angles and does not feature a fixed right angle or graduated blade. The pipefitter's square is similar but is specifically designed for use in the piping industry and may not necessarily have the graduated markings typical of a try square. Thus, the unique characteristics of the try square make it the correct answer for this question.