Name some examples of hacks outside of computing

In the days of early payphones, there was a sound that would play into the phones which signified that you could make a phone call, and since the cost of the phones was expensive at that time, people would record the sound that needed to be played, and play it into the phone so they could make calls for free.

Explanation:

Idk if this counts as hacking outside of computing but i hoped it helped :)