Amazing Facts - Reasons are surprisingly awesome

What is the reason for holes on top of pen caps?

Usually most of the pens with caps have hole in its cap and the reason behind it is surprisingly awesome. Here is the reason: 

They say roughly 100 people die in United States each year from choking on pen lids with no holes on lids. Hence the design of the pen was changed as a part of international safety standards in creating the caps. This way, even if someone accidentally swallows a pen cap, he/she can avoid suffocation due to hole provided in the lid.

Why are Airplane(Aeroplane) windows round?

In Square windows, sharp corners are naturally weak spots where stress concentrates, weakened further by air pressure. When subjected to repeated pressurization, four corners on a square window spell disaster.

Curved window panes, on the other hand, which have no focal point, distribute that stress, reducing the likelihood of cracks or breaks. Circular shapes are also stronger and resist deformation, and can thus survive the extreme differences in pressure between the inside and outside of the aircraft.

Here is a question for you guys:

What is the purpose of the small pinhole found in many locker locks next to the keyhole?