The padlock’s tiniest hole
Do you use a padlock outdoors? If so, do you change padlocks often due to rusting or freezing up in the rain or snow? Perhaps you haven’t noticed, but there is a tiny hole next to the keyhole on the bottom of almost any padlock that is meant to save you time and money.

Believe it or not, this tiny hole at the bottom is there for two reasons. First, it acts as a filter in case of extended water exposure, so it won’t rust in the rain or freeze and break during the winter. Second, it is used to pour engine oil inside, which allows the key to turning in the lock without major complications. If the padlock does not have this tiny hole, then it is better to only be used indoors.