Abstract: A device for locking a guitar strap to a guitar has a slotted base with one slot for receiving a guitar strap through it, and a second slot for mounting to the strap peg on the guitar. The second slot is keyhold shaped and has an entry portion and a retaining portion, the entry portion being large enough to receive the head of the peg, and the retaining portion being narrow enough to prevent the peg head from passing through it. A slot blocking lid is hinged to the base and pivotable about the hinge to close so that the entry portion of the slot can be blocked when the peg has been received in the retaining portion of the slot. A retainer strap is secured to the base at one end remote from the hinge, and extends through a slot in the lid, also remote from the hinge, and fastened by a snap fastener adjacent the hinge to hold the slot blocker lid in locking position until the retainer strap is intentionally released.