-How to use basic hand tools efficiently and correctly (wrenches, soldering iron, etc.)
-Bayesian inference
I do not know what you mean by "use a wrench correctly". I mean, I do not see how a person can use a wrench incorrectly.
Can you hint at what I am missing?
ADDED. There is a widespread standard for which way to turn to loosen a bolt and which way to turn to tighten it. Maybe that is what you refer to.
ADDED. If you use the wrong size wrench (i.e., slightly too big) you can "strip" the bolt (i.e., turn the hexagon into a circle, thereby making it impossible to wrench the bolt in the future even with a correctly-sized wrench). And as Romeo...
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.)