Step 3: Fit The Bit to The Keyhole

filing down the bit on the key to match the keyhole in the existing lock, making a new skeleton key for an old mortise door lock
Photo: Kolin Smith
If the bit is too long, mark where it hits the bottom of the keyhole. Using a file or a bench grinder, as shown, remove just enough metal from the bit's lower edge for the bit to pass through the keyholes on both sides of the lock.
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    Tools List

    • bench grinder
      Bench grinder (optional)
    • warding file
      Warding file
    • table vise

    Shopping List

    1. Penetrating lubricant, such as WD-40