Cutting the Slot

On the left is a key with its original back rail hole. Draw the lines shown on the illustration onto the key. The space between the 2 lines should be the same as the diameter of the back rail hole. A scroll saw with a #7 blade is the best tool for making these slots, but a bandsaw will suffice if a scroll saw is unavailable. Cut inside of these lines (leave the pencil lines) from the rear edge of the key all the way to the ledge formed by the rabbet. Nibble away the material between your two cuts. Your key should now look like the key on the right.