Removing and installing mechanical fasteners (bolts and screws) is more complex than you might assume. It goes far beyond selecting the right size tool, and turning it in the correct direction.
A mechanic develops these skills gradually over decades- a master mechanic would often have no trouble removing a corroded bolt that a novice mechanic would destroy for example. Conversely, they can also install a bolt in a manner with less chance of failure down the line.
Some (but by no means all) of the issues involved include:
As someone who operates vehicles in remote areas (offshore boating, remote desert driving) skill in using hand tools has made potentially terrible situations much better and possibly saved my life many times...
So, transferable skills: skills that, upon improvement, increase your ability in other areas (and also improve other, higher-level skills).
A basic example would be reading/writing. Knowing how to read and write allows one to access a huge amount of other skills and resources which are otherwise unavailable. A less obvious example would be clear speech (enunciation). Ability to speak clearly improves one's prospects in a lot of different areas (e.g. professional advancement, dating, etc.).
I'm looking for additional examples. Which skills did you find to be most transferable? Did you become proficient in X, and then found this helped you in many other areas of your life? Please share.
(I tried to find whether this was discussed before, and failed; if it was, I would appreciate the link.)