The valve is the source of gas to the burner. There are both single and dual valves sending gas to single burners, dual (chamber) burners and two burners. The output of a valve is through an ORIFICE of a precise size that relates to the type of gas being used: LP (Liquid Propane) or NAT (Natural Gas), among other things.

The orifice can get plugged by tiny spiders spinning webs in the opening. This will cause the grill burner to not supply enough heat for proper cooking and possibly cause a gas backup and "flashback" fire behind the control panel.

Cleaning each orifice is a necessary part of normal maintenance if you live where there are spiders. (1.) Lift the burner and venturi away from the back of the valve. (2.) The orifice is removable with an 318" wrench as shown above. Close examination can reveal web structures in the orifice and in the valve tube. These can be cleaned out using a wooden toothpick, a cotton swab or a blast of air. DO NOT USE A NAIL, A KNIFE OR OTHER SHARP METAL OBJECT THAT COULD CHANGE THE SIZE OF OR DAMAGE THE ORIFICE.

After replacing the orifices, clean out the venturi tubes before positioning them back in place over the orifices. Clogged venturi can lead to "Flashback", where a gas build-up in the venturi catches fire behind the control panel.