The Rule Stop has an anodised aluminium body with a brass locking screw. The Rule Stop fits onto virtually any standard steel rule between 22mm(7/8") and 30mm(1.3/16") wide. Once fitted to your rule, precision machining ensures the body is always square to your rule's edge. Effectively, it allows you to use a rule in a similar way as you would use a combination square. You can scribe lines parallel to the edge of timber, or use it as a depth stop, a transfer gauge, a small square and a useful tool for setting sharpening jigs. The Rule Stop is real gem, invaluable for accurate marking out. It is easy to align the edge of the Rule Stop with engraved scale graduations. The brass locking screw won't damage your rule's edge. The knurled knob is 15mm diameter making it easy to tighten without it getting in the way of the stop's functions.