I work as a technician in a factory that produces Nickel alloys. One piece of plant we have is a rather large automated extrusion press (turns yer machined billets into bar, section, seamless tube). Because of it's automated nature it has a number of CCTV's dotted around that feed back to the control cabin.

Call came in one day asking me to check one of the monitors, picture had gone doolally. "Groan!" I hate going down there 'cause you can almost guarantee that during a breakdown the crew would be crammed into the cabin, making the working conditions difficult (if not intollerable).

Get there and sure enough everyone's sitting around yacking (and presumably thinking they're about to have a nice little unscheduled break). I walk in, go straight to the monitor, whose picture is nothing but snow, give an almighy thwack on the side and lo and behold, much to everyone's surprise (including mine) the picture returns.

Cue a number a moans and groans from the disappointed crew. "They pay you all that money just to do that?"
"Ah," says I. "You've got to know where to hit it," and walk out.