What is a king valve in refrigeration?

When referring to the "king" valve, most air conditioning technicians are referring to the valve which is found downstream from a liquid line receiver. It is also commonly referred to as a liquid line service valve or an isolation valve. The name King valve is what Carrier calls its service valves. If you call a wholesaler or manufacturer for a king valve the answer you will receive is "Sir, we don't carry king valves." Every manufacturer calls service valves something different.