To maximize the metal you have to work with, try to avoid cutting too much into the flat part of the can’s side. Instead, err on the side of the taper. Take your time when cutting the shims. The straighter and smoother your cuts, the better your shims will work. You’ll also be able to make more shims per can if you’re careful with your cuts.
Using a shim takes a bit of practice. It’s easy to bend them or tear them in the small space between the shackle and the locking mechanism, and it can be hard to get them into position. Fortunately, you can make many shims out of a can, and once you get the hang of it, the process will become much easier. Just don’t try to force anything, because if you get a piece of the shim stuck in the lock, it will make your job even harder. Once you have driven the shim into the shackle housing, take the tabs you created and pull on them from side to side. Even if the shim itself doesn’t move, this motion is vital to opening the lock. Some locks require that you insert a shim into both sides of the shackle (both holes where the shackle enters the lock). If you can’t seem to get the lock open with one shim, try two. Once you hear a click similar to that of when you pull an unlocked shackle out of its housing, the lock will be able to be opened.
