Tricks of the trade
For every occupation, there is a catalog of secrets only its employees are aware of—such as how waiters with heavy platters know to look straight ahead, and never down. Here's a whole list of such tricks of the trade, some of them rather amusing. (And of course we've been using the term PEBKAC for ages).
»Nurse
Patients will occasionally pretend to be unconscious. A surefire way to find them out is to pick up their hand, hold it above their face, and let go. If they smack themselves, they’re most likely unconscious; if not, they’re faking.«
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