left handed screwdriver

when your fellow tradies are out on smoko and they ask the new apprentice to give them a left handed screwdriver, it's both a prank and an intelligence test to check if he knows his tools.
It's a more generalised version of the 'muffler bearings' prank that car mechanics often ask from new trainees.

Tradie: "Oi Jimbo, can you go down to bunnings to grab me a left handed screwdriver?"
Apprentice: "Sure, but have you found the muffler bearings yet?"