line in the sand 

Something that you refuse to do, or something on which you will not compromise. A point that you will not pass in any situation.

I've already apologized multiple times. I'm not texting her again. That's my line in the sand.

line in the sand by mark.101 September 11, 2012

Sand in the Line 

When non-American people are serious about getting a task done The reverse of the common term "line in the sand" makes every one know you mean business and that you are the "boss".

Steve #2: Lisa, I am drawing a sand in the line for this to be completed by Friday.

Sand in the Line by sausagefest12 March 11, 2019