The case latches on many guitar cases are held on with split rivets. These are rivets with a head on one end and a two-pronged (or "bifurcated") shaft on the other. The rivets typically used for guitar cases are larger than many industrial rivets, making them easier to work by hand without having to use a welding torch. You will need some common hand tools, and, of course, the right sized rivets. But with those in hand, you can install or replace the split rivets in your guitar case in just a few seconds.
Hold the latch in the position you want to install it, with the guitar case closed. The opening where the top and the bottom half of the latch come together should be positioned over the line where the top of the case overlaps the bottom. Use a piece of chalk or white crayon to mark the position of the mounting holes onto the case.
Drill the mounting holes through the side of the case, using a drill and 1/8-inch bit. Drill from the outside of the case.
Reposition the latch over the holes, and place a split rivet through a mounting hole in the latch, and through the matching hole in the case. Hold the rivet in place by pressing down on the head with your finger.
Place the length of the blade of the knife into the split in the rivet, which is inside the case. Twist the top of the knife to left so that the left half of the rivet shaft bends at a 90 degree angle outward. The top of the blade will put pressure on the left-hand prong, while the edge of the blade will wedge at the base of the right-hand prong. Twist the top knife to the right to bend the other half of the rivet shaft at an opposite 90 degree angle.
Place the flat of the blade across the two bent halves of the rivet shaft. Using both hands, press the blade from the inside of the case and the rivet head from the outside of the case until the rivet tightens.
Repeat this procedure for all the mounting holes in the latch.
This same procedure can be used to mount handles and hinges on the case as well. If you're simply replacing the rivets or the latches, you don't need to drill new holes in the case; just use the existing holes. If the mounting holes in the case have become damaged, you may need to use a longer (not thicker) rivet; this will spread the prongs wider to grab on more solid portions of the case body. Rivets are made in stainless steel and brass-coated steel, to match the metal finish of your guitar hardware.
Be very careful not to cut yourself when using the knife to split the rivet shaft. Position the knife as far down in the case as possible so that little of the blade will be exposed above the case edge.