Emphasizes extensive knowledge about intricate details of a subject or a system. The mechanic knows that car inside out; no one else should touch it.
Pro Tip 2/3
Expert Implication
Implies a level of expertise or professionalism in a particular area. She knows the software inside out and can solve any issue that arises.
Pro Tip 3/3
Not Literal
It's a figurative term; you don't actually see the inside of a topic. Despite the name, health inspectors don't actually know every restaurant inside out.