What is the function of a try square?

The try square is a versatile tool primarily used in woodworking and metalworking for ensuring accuracy in construction and layout work. Its primary function is to check square corners, ensuring that both edges of a piece are at a right angle to each other. This is crucial for maintaining precision in projects, as misaligned corners can lead to structural issues or aesthetic problems in the finished product.

Additionally, try squares can be used to measure angles and mark straight lines. The blade of the try square is typically straight and can be used to draw lines that are perpendicular to the edge of a material. This is particularly useful when laying out the dimensions of a piece effectively.

Because of its multi-functional nature—checking for squareness, measuring angles, and marking straight lines—the try square serves as an essential tool in various applications within woodworking and general construction. The combined capabilities of the try square justify its classification as a tool used for all these functions, making the answer "D" the most encompassing and accurate choice.