With this tool, you'll be able to repair the telephone line cord that connects between your phone and phone jack, if the phone line cord has become partially or completely detached from the modular plug connector on either end of the cord somehow. This tool crimps a new modular plug onto the end of a phone line cord. You can also create your own custom length phone line cords this way with any RJ45 (4-line) modular plug connectors to be crimped onto RJ45 phone line cords. So you can use this tool to add a phone jack to your phone wire or repair your broken one. Compared to $29.95 at Lowes or Home Depot.