US Patent 7131302 Keyway plug for safe deposit locks

A keyway plug that discretely provides a device for preventing a person from unlocking a tumbler lock even if the correct key is used. The present invention includes a plug member that is sized to fit entirely within a keyhole and is effective to block a key from being completely inserted into the keyhole. The plug may be removed from the keyhole through use of an extraction tool having a magnet which attracts the plug and magnetically couples the plug to the extraction tool when the tool comes into contact with the plug.