Are shutoff valves screw on or sweat on

[vegashomes]

How can I tell if my sink shutoff valve is sweat on or cam it be threaded

[Redwood]

You would have to look and see. You would also have to know what you are looking at.

Post a picture!

[hj]

They screw on, sweat on, or use a compression joint. Which one you have is obvious by looking at it, so if you cannot tell, then you need a plumber before you damage something.