The 45° Mag Square is a small magnetic base square. It has standard measurements on one side & metric on the other. The lip on the bottom allows for scribing 45's on 2x4's. It is also great for setting blade heights, & for setting 45° & 90° blade angles. The magnetic base sticks firmly to the cast iron or metal table & allows hands-free adjustment of spindles, blades & fences. The built-in scale allows you to easily set the height or do precision layout for finish carpentry.