Adding a Key-Holed Ruler to Your Bench
You can mount a removable key-holed metal ruler on the front edge of your workbench, for both easy measuring on the workbench and for easy access for measuring and marking projects elsewhere. Simply drill keyholes (a larger hole with an overlapping smaller hole above it) in two locations along the ruler. After drilling the keyholes we sanded them smooth to get rid of the potentially dangerous sharp edges. Next, drill appropriately sized screws (ones that will fit into the smaller sized keyhole) to the front of the workbench and use the keyholes to mount the ruler to the bench with screws.
Also, it is important to note that we placed our screws in a location in which the ruler would lay flush with the edge of the workbench. This makes it extremely easy to use the ruler for quick project measurements because of its convenient location.