A radiator valve with a covered stem that requires a special key or tool to adjust. Installed on the return side of a hydronic heating radiator, it is used to balance the system by restricting water flow. Once the technician sets the flow rate to ensure all radiators heat evenly, the cap is replaced so occupants cannot accidentally tamper with the balance.
Heard on the job
The bedroom radiator is barely getting warm so I need to open up the lockshield a quarter turn.
Insider tip
Never use the lockshield to turn off the radiator for maintenance unless you count the exact number of turns it takes to close it, so you can restore the balance later.
Also heard as
- lockshield valve