Designed specifically for working with dimensional constuction lumber, the Shinwa three dimensional clear mitre square has pencil holes for dividing into halves for lap joints, thirds for M&T's bridles etc, quarters for finger joints as well as edges for 90° and 45° cuts.
For absolute measurements the square end has metric graduations starting from the inside corner and there is a 150mm scale on the long edge and there is a cutout window so you can mark perpendiculars close to the other end while still working from your face side / edge.
Made from clear polycarbonate so you can see your marks through the square and have a better chance of avoiding knots or defects in your joinery.
The main body of the tool from the square edge to the cutout is 3½" wide, so you can see an even overhang either side regardless of whether you are working with sawn timber, PAR, CLS etc.
An astonishing amount of functionality squeezed into a superficially simple object.