The 45 MagSquare 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 setting45 & 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.