Jolly Rodgers wrote:when shimming padlocks pop can shims usually wont work. you either need stronger material or commercial shims.
I disagree, I've had great luck with pop can shims, granted I have to use them in a somewhat unconventional manner. I insert the shim like normal on the opposite side as the latch and take a pair of pliers and grab hold of the shim making sure its wrapped tightly around the shackle and turn with the pliers.
Another helpful hint is if you have trouble inserting a pop can shim is to sand the paint off which helps make them a lot thinner but just as strong. That being said, if you don't have time to sand pop can shims for 1-2 uses, professional shims are nice to have.