Temperature is controlled in a surface burner by varying the flow of gas to it with a manual gas valve. Ignition is achieved in one of two ways; either a standing pilot flame or a spark ignition. Gas shoots out of jets on the side of the burner and into a flame tube, which carries the gas to the ignition source. The flame then chases the gas back up the tube to ignite the burner. (See figure 5-A) This allows two or more burners to share the same ignition source. Some burners have an ignitor built in.