That meant extra work, as the original system had no lockshield valves
and all but two radiators were fed and returned from a single corner
(the valves had both flow and return connections and used an extension
pipe within the radiator to get the feed to the far end. As copper was
put in, the self-balancing of the carefully sized piepwork was
disturbed and feed and return had to be separated to opposite ends of
the radiators to allow lockshields to be fitted.

SteveW


The Lockshield was under a domed cover and was a screw. I thought they were
quite good - but never a thermostatic version so they were doomed.