You see them in the museums around the Chesapeake Bay and a few of the really, really old seafood or crab houses in Maryland. They were used for commercial waterfowl hunting from little low lying boats (punts). They'd take out large numbers of birds sitting on the water or just landing usually. The birds were mostly shipped to NY City.
Maryland law still lists them as an illegal device, though they haven't been common since at least the 1920s.