Which tool is most appropriate for marking straight edges?

The combination square is the most appropriate tool for marking straight edges because it is specifically designed for this purpose. It typically consists of a ruler with a movable head, which allows for precise marking of straight lines at various angles, including 90 degrees and 45 degrees. Its accuracy and versatility make it essential for tasks such as woodworking, metalworking, and construction, where precise measurements and straight edges are required.

The other tools listed serve different functions. A compass is used primarily for drawing arcs and circles, not for marking straight lines. A chisel is a cutting tool used for carving or shaping materials, and it wouldn’t be effective for marking. A grease gun is designed for lubricating machinery and has no relevance to marking or measuring tasks. Thus, the combination square stands out as the best option for creating straight edges.