An envelope with a transparent panel showing the address printed on the letter inside is such an ordinary object that the question of why it exists does not usually arise.…
The small metal plate at the base of a stapler, the one the staple legs hit, is called the anvil, and on most staplers it rotates.
Turn it and the…
Look at the cap of a cheap ballpoint pen. There is a small hole in the top of it.
Most people assume it is a moulding artefact, or something to…