Gas tap

Although a gas tap may be a valve that releases any gas, the word is most commonly used to refer to taps that control the flow of fuel gas (natural gas or, historically, coal gas, syngas, etc.) in the home (for gas fires or other appliances) or in laboratories (for Bunsen burners). Inside the tap a tighly fitted (brass-only versions had to be greased once) cone with a cross bore has to be aligned with the in- and outlet-line to open the valve. The handle is longitudinal and parallel to this bore, that one sees the status of the valve. It can be closed quickly but does (nearly) not work to regulated the amount of flow. [Tap (valve). Wikipedia]