Padlock holes are drain holes
You may have opened many doors in your life (physically and metaphorically), but looking closely at a padlock, you will find a teeny-tiny hole towards the bottom. Some padlocks, particularly those designed for outdoor use, may feature a small hole in the cylinder slot’s side. But, do you have any idea what it is for?
One of its many duties is to keep the padlock mechanism in good shape over time by releasing water that may otherwise stagnate owing to high humidity or freeze inside the padlock in cold weather. Moreover, this little hole is used to pour oil into the lock so that it does not get jammed up or to lubricate the internal mechanism if it is rusted.