A lot of people probably have greenhorns working for them for the summer. Many of them are spoiled kids, boss's family or other unworthies good only for hazing. So get them good.
First you prime them. Send them after the prop wash, or the left-handed crescent wrenches, or send them back to the warehouse for screws with heads on the other end ("These go on the other side, stupid!"). After hours, take them on a snipe hunt.
Then when it looks like they start to suspect an inkling of a shadow of a clue, send them to the store to get you a DVD rewinder.
Yep, someone is selling them. Thanks to Gizmodo for telling us, I think.