draw the line at something—refuse to do smth. because it is more than one is prepared to do:
- I draw the line at nappychanging, not because I am a man but because I don’t like surprises of that nature.
draw the line under something—try to forget about a bad situation, etc., so that one can start again:
- Vicky and I agreed to draw the line under our disagreements and try to look towards our future together.