MusicNomad Acousti-Lok MN 271

If you need this device, it can "save your life" or at least guitar.

+it does what it is supposed to do - allow you to use original schaller strap locks with the acoustic guitar jack output (like L.R. Baggs) without need to drill another extra hole for the knob in the precious guitar body.

-not sure if it can work with anything else than schaller. also don't confuse with other jack types (i think it's MN270 and MN272). some will also consider this solution useles and rather put extra knob next to jack output, or don't use strap locks at all. some will never sell their precious expensive guitar so they are not afraid of drilling. but I wanted to keep my instrument as clean as it was produced.