What is a keyhole router bit used for

Optimal slot dimension for skirt support structure of coke drums keyhole slot dimensions Making a keyhole slot requires that the router bit be plunged into the work and then moved a short distance before being backed out and removed It's always a keyhole slot dimensions 60mm x 90mm Keyhole has a circle diameter of 29mm, and slot width of

keyhole slot bit I decided to make my jig 3-12 x 4-12 so I would have a 1-inch span to slide the router back and forth to cut my keyhole slots