Cucumber slicers allow a cook to create very thin, uniform slices of cucumber to be used for sandwiches, salads or garnish.
There are two different types of cucumber slicers.
One is a round device turned by crank, that you clamp to a table and press the cucumber through with a pusher. Original ones were made of cast iron. You can also slice carrots with these.
Another type is a flat, rectangular surface that you drag the cucumber over. It looks like the bottom of a wood plane, or a mini-mandoline, in that it has a metal blade on an angle. Some have two blades on them. Antique ones were made of wood; more modern ones are made of metal or plastic. Metal ones may have the blade built into them, rising out of the metal. Older ones had adjustable-angle blades.
Erlanger, Steven. Unkindest cut over a humble cucumber slicer. New York Times. 5 October 2002.