This stout little ruler is exceptionally useful for everyday shop tasks like setting up bit and blade heights and router table fences. With graduations on all four edges and perfectly square corners, you need only set it on edge and raise your router bit or move your fence until you reach the right setting. The same features make it great for marking out joinery, since all edges are square to one another. It's also ideal for marking out turnings at the lathe, due to its short length. The size is perfect for an apron pocket, and at 1mm thick, it's sturdy enough to stand up to the hard knocks of shop life.