What is an adjustable carpenter's tool that aids in marking angles?

The combination square is an essential tool for marking angles because it features a ruler and a movable arm that can be adjusted to various angles. This versatility allows users not only to measure and mark precise angles but also to check squareness and perform measurements accurately. The combination square is highly valued in woodworking and carpentry for its ability to provide reliable and repeatable measurements, which is critical when working on projects that require precise fit and finish.

While tools like the framing square and protractor also assist in marking angles, the framing square is generally more suited for larger framing tasks and does not have the adjustable feature that the combination square possesses. The protractor, on the other hand, is primarily designed for measuring angles rather than marking them in practical carpentry contexts. The chalk line serves a different purpose by marking long, straight lines across surfaces, making it less relevant when specifically marking angles. Thus, the combination square stands out as the adjustable tool specifically designed for marking angles in carpentry.