Radiator lock shield valves are the small valves on the other side of the radiator from the TRV valves (the ones with the 1-5 dial on). The can be used to ‘switch off’ the radiator effectively taking it out of the heating loop such that no hot water is pumped through that particular valve.

Here’s which direction to turn the valves:

• Turn anti clockwise to open
• Clockwise to close

The best tool to use is a small set of mole grips. Be careful not to over tighten these valves, you don’t need much pressure at all to close them.