An indispensable accessory for acoustic guitars with large endpin jacks. The Strap-Keeper strap lock attaches first to your strap, then to the endpin jack on your instrument. The nylon clip then locks it in place so that it cannot come off the button. These are designed for the typical endpin jack buttons used by Fishman, L.R. Baggs, and others, but not the smaller diameter jacks found on factory install systems used by Yamaha, Takamine, Ovation, and Taylor Expression system.