I have Suntemp hot water baseboard radiators. Some rooms I don't heat at all so I close the vent but some heat will get out of the radiators. I took off the end cap and see a control mechanism of some sort. It's just a screw.

I read in a handyman book that these radiators are adjusted when installed so that rooms with not enough heat- the water entering the radiator will be increased and other rooms decreased, apparently by turning the screw. I read somewhere that you can't close it off entirely- which is fine but I'd like to close it off as much as possible.

I'm hesitant to touch any plumbing or electrical stuff as I know next to zero about these subjects.

I should think that turning the screw clockwise will close it.

Any comments will be appreciated.
Joe Z.