A gas hob is a type of appliance that uses burning gas to heat and cook food. For operation, it requires a connection to a natural gas supply or a propane-butane cylinder. The temperature of each burner is continuously adjusted using rotary knobs, which instantly change the flame size. The hob's surface can be made from various materials, such as stainless steel, enamel, or tempered glass, which affects its appearance and maintenance requirements. Modern hobs typically include safety devices that automatically stop the gas supply if the flame is unintentionally extinguished.