4. Why you may need a hole and serration at the end of a tape measure
The hole is intended for the user to attach it to a nail or bolt and measure the distance.
The serrated end will help you mark the place you need if you don’t have a pencil handy.
5. Why there is a hole at the bottom of a lock
Padlocks are generally used outside, and this hole is drainage for water that gets inside the lock when it rains — otherwise the lock would become rusty. It’s also convenient to oil the lock through it.