What tool is most commonly used to break and trim masonry units?

The tool most commonly used to break and trim masonry units is the mason's hammer. This tool is specifically designed for working with masonry materials, providing the necessary weight and control to effectively chip away or shape bricks and other masonry units. The design of the mason's hammer, which typically features a square head on one side for striking and a chisel-like edge on the other for cutting, makes it ideal for achieving precise breaks or trims on masonry.

While other tools like chisels can be used for specific applications, they are generally used in conjunction with a hammer to assist in breaking or shaping masonry. A utility knife is more suited for cutting materials like drywall or insulation, and a brick saw, though useful for making longer and more accurate cuts, is not typically used for quick breaking and trimming tasks. Therefore, the versatility and function of the mason's hammer make it the best choice for these types of tasks in masonry work.