Abstract: A door preparation drill jig is usable to prepare a door to receive a lockset provided with through-bolt mounting studs in a main bore provided in the door. The drill jig has a planar body, drill guides, and a cylindrical body. The front surface of the planar body has a portion for the placement of installation instructions and the attachment of a C-clamp. Each drill guide is arranged to receive a drill bit used to drill one of the mounting holes for receiving a mounting stud of the lockset. The cylindrical body has a chamfered edged latch slot which receives a portion of the latch extending into the main bore of the door. Additional tabs appended to the cylindrical body flex to ensue the chamfered edges around the border of the latch slot firmly engage the latch in the main bore and another flexible tab flexes to ensure a tight fit of the jig in the main bore of the door.