Most plain knives are sharpened using the Tru-Hone system (an American sharpening machine which is portable and clean to use).
The machine has two counter rotating grinding wheels, sharpening both sides of the blade at the same time, which are adjustable for grinding angle and for speed. A three stage process is used for every knife. The first stage is to grind the knife until it is sharp, the second stage then strengthens the actual cutting edge, whilst the third stage hones the blade using a slower speed. Heavy chopping knives and meat cleavers use the same process but the blade angle is different.
Knives which have suffered an 'accident' can be reshaped and then sharpened. This needs to be done back at base using a belt system or on a bench grinder.
"Hand of limpid waters where lofty mountains reign." - A Matthews