There's a classic well-illustrated book, _How to Keep Your Volkswagen Alive_, which spends a whole illustrated page at the beginning building up a reference frame for working on the vehicle. Up is sky, down is ground, front is always vehicle's front, left is always vehicle's left.

Sounds a bit silly to write it out, but the diagram did a great job removing ambiguity when you expect someone to be laying on the ground in a tight place looking backwards, upside down.

Also feels important to note that in the theatre, there is stage-right and stage-left, jargon to disambiguate even though the jargon expects you to know the meaning to understand it.