The water supply line to my icemaker is leaking under the sink, not a small leak, a considerable leak. I cannot get filtered water from refrigerator, cannot use any cold water at all in kitchen and I don't have cold water for washing machine with the cold water inlet turned off. I need a temporary fix until Monday. Do you have any suggestions? If it will be a couple of days before you are able to answer, I will have done something already. Thank you anyway.

You should be able to turn off the valve that is used to attach the refrigerator line to the water pipe.
Post pic.

We answer as soon as we can, Sounds like you're leaking from the self piecing valve on the sinks cold water supply. For a temporary fix sop you can use the cold water here's what I would do, Remove the selfpieceing valve. You will be left with a small hole in the supply line. Now take a small piece of rubber, like from a old inner tube and place it over the hole Purchase a small hose clamp to secure the patch. Tighten it down and turn the supply back on. Check for leaks. You now have cold water for the weekend but no water to the fridge.
Monday you can repair the hole by clearing the water out and patching the hole with solder or simply replace the supply.
You are now back to square one. If the old self piercing valve's OK you can install the icemaker or purchase a new valve. Good luck, Tom

If the valve won't close properly and is not leaking out of the pierced hole, you can turn the valve down as tightly as possible and use a 1/4 compression cap on the fitting end. Did this last week and no leaks.

Depends how it is connected to the supply line. Can you explain further - or post picture of it. Back to you. Milo