Some acoustic guitars have a single strap button on the tail, but have no spot to attach the strap to the top of the guitar. This is a common point of confusion for beginners, but one that is easily rectified. Ready-made strap loops for acoustic guitars are available at most music stores, but you can make your own with a shoelace or similar type of cord, and it is easily fitted to a standard guitar strap. This system is safe and effective, and used by acoustic guitarists who do not wish to modify their instruments by drilling a hole for an additional strap button.
Fold the shoelace in half and thread the looped end into the hole on either end of the guitar strap. This is an easier method than threading a single string end and tying a knot, and the double string thickness adds an extra measure of security.
Thread the two loose ends of the shoelace back into the shoelace loop and pull taut. The shoelace is now firmly attached to the strap, with the two loose ends hanging free.
Insert one of the loose ends onto the top of the guitar neck, underneath the strings, just behind the string nut. The string nut is a white plastic piece that is elevated and suspends the strings over the guitar's fretboard.
Tie the two loose ends together with a knot of your choosing, and pull slightly to test for strength and slippage. The type of knot does not matter, but should not be movable or slip-knot, or one that can be easily removed. The knot may be doubled-up for added security.
Attach the other end of the strap to the guitar's end-pin or strap button, located on the tail end of the guitar. The strap slips over the end-pin or button, which is tapered to prevent the strap from slipping off. End-pins and strap buttons serve the same purpose, which is to secure the strap. End-pins are inserted into a hole in the guitar and held in place by friction, while strap buttons are held in place by a screw.
New straps may be stiff and the holes may be difficult to attach to the end-pin or strap button. A bit of patience and careful work will eventually result in securing the strap. Use a standard, adjustable guitar strap for best results, rather than retrofitting a belt or cord. Inexpensive guitar straps are available at any music store.
Don't cut the strap hole to make strap button or end-pin attachment easier. The widened hole may cause the strap material to weaken and tear. Avoid installing strap buttons or end-pins on your own. Drilling holes in the wrong spot on an acoustic guitar can cause damage to the finish, wood and internal bracing. Guitar modifications should be entrusted to a professional repair shop.