If you take any padlock and look at the bottom of it you will realise that there is a very tiny hole. This hole is next to the hole for the keys and is different from it. This hole serves many functions and without it, a padlock is prone to several underlying negative conditions that can either destroy it completely or partially. You may think that this hole serves no purpose but if you continue reading you will come to find out that it is not there for the sake of staying there.
First, this hole is designed in a way that allows water to drain off. When water gets into the padlock, you know what will happen next. The water will induce rusting and the padlock will rust. But with the hole in the padlock, no rusting will occur because the moisture will be drained off.
If your key is not working in the padlock, put some oil in the padlock. This is another place where this hole will be of benefit. You are advised to use the tiny hole rather than the hole for the keys. If you do this the padlock will start working again straight away. These are the two major functions of this hole. If you know the third function, don't hesitate to mention it.