Getting a Handle on Handles

zvalve

Or an alternate title “If It Ain’t Broke Don’t Fix It”. First off, the radiators seem fine and producing ample heat with no leaks. The radiators are finned tubes in a convection box partially recessed in walls under windows connected to a hydronic boiler. However, there is only one shut off valve handle which in the photo shows a square depression which mates with a square piece on the valve shaft that has a 1” protrusion off one side in addition to a cylindrical hole beneath the square depression. The longest radiator in the living room beneath bay window has no valve. Valve handles available on line or in stores have square openings which don’t fit the valve stems I have exactly. My stems seem flat on opposite sides and rounded on the two other opposite sides. The valves are Shure Flow and some of the valves seem frozen so I don’t want to put a channel lock or vice grips on the stem to close or open valve for fear of breaking the valves. Can anyone illuminate the chaos here. Should I even bother to get handles or turn them off. Might be good to shut off heat and valves in rooms not getting used for extended periods, no?

nicholas bonham-carter

Let’s see what the other end of the radiator looks like. Sometimes these have been piped in series, and turning off the first in line shuts off more than one.
Since radiators are placed next to outside walls, there could be a danger of freezing if turned off. A TRV might be a better solution for seldom used rooms.—NBC

HVACNUT

If they are all working, then leave them alone. That's a can of worms you don't want to open until have a couple free days to spend replacing them. 
Looks like a monoflo system so the bleeders on the convectors should work if needed. 

STEVEusaPA

What's the piece of plywood for?

zvalve

Steve the plywood was for resting paint cans and tools on so they wouldn’t damage floor. Thanks everyone for comments. Nick and HVACNUT how would I know if the system is in series or monoflo? The pipes going up to radiators are covered in basement by sprayed on insulating foam around foundation sill plate and band joists.