This is an example of one of the most common requests for modification. “I want to install a pick-up, but I don’t want to drill any holes in the guitar. And I would like to return it to its original condition when I want to.”
You can secure an output jack with tape or some kind of putty, if you only use the pick-up once or twice. But for the performer who moves around on stage or if it is meant to be a long-term installation, then the taping method is not sufficient. You have to think of a more reliable way to secure the pick-up. In this case, we made a jack holder using a brass plate, but we used the same screw holes.
What about the wire from the pick-up? If you don’t want to drill any holes, taping it down on the top is the only way. If the bridge is glued on top, drilling a tiny hole under the saddle is the most common method. But if the bridge is floating, like on an archtop guitar, it’s hard to say which way is better.