A sommelier knife, waiter's friend or wine key is a corkscrew in a folding body similar to a pocket knife. It was conceived by the German Karl Wienke in 1882 and patented in Germany, England, and America.[1]
An arm extends to brace against the lip of the bottle for leverage when removing the cork. Some sommelier knives have two steps on the lever, and often also a bottle opener. A small hinged knife blade is housed in the handle end for removing the foil wrapping the neck of many wine bottles.