To ripen green tomatoes at the end of the season, cut off the stems holding the green tomatoes, and hang them on a string in a warm place. They will ripen on their own over a few weeks.
My very good mother did this in my storage room. She used a clothes line tacked into the wall studs. Then she draped the vines over the line, no clothes pins or clips or anything.
2 weeks later, ripe tomatoes were waiting for us! And I didn't have to lose the fruit to cold weather!
All the best!