Taps are used for the purpose of letting off or stopping at pleasure
the flow of liquids from vessels or through pipes. The forms of
stop-cocks are very various, but the form shown at fig. 1 is by
far the most general; it consists of a short curved tube, having an
upright cylinder in the centre in which a plug with a handle turns;
this plug is perforated in the direction of the length of the handle,
so that when this is turned crosswise the communication is shut
off (figs. 2, 3, and 4). The “nose” or end of the tap is sometimes
prolonged into a spout, for filling bottles, &c., as in fig. 5.