Golf Rules – Can you borrow someone else’s golf equipment?

Basically yes you can, unless it is clubs they have selected, or their ball in play/ball they are required to put back in play.
So tees, balls, pitch repairers.
The One Ball Rule is one that can be applied, and is on a few professional tours. That is one where you must use the same make and model of ball. However, you won’t find it in many club events.