Check the listing for details. Liftmaster 841 LM Automatic Power Garage Door Slide Lock. Condition: Open box. Listed at 54.99 USD. The LiftMaster 841LM Electric Slide Lock is a reliable and efficient track mounted automatic deadbolt designed for residential use. With ten feet of wire and a three prong plug this 12V lock is compatible with all newer side mounted Liftmaster and Chamberlain residential garage door openers and all LiftMaster and Chaimberlain belt and chain drive openers with plugs on the opener head next to where the eye and wall button wires connect as shown in photo. This model 841LM (001D8875) includes screws and mounting templates for easy installation. Stick template to the track to where large hole is slightly above garage door roller. Up to two slide locks can be installed per opener for a super secure addition to any garage door setup. Note: Manufacturer date may vary.