the point at which any decision is made final and no "bright ideas" should be considered that would change the final decision
Person 1: "We are going to the beach for summer break."
Person 2: "That's great! I was also thinking we could stop at my parents house . . ."
Person 3: "And then we can go to our sorority sisters place for a visit . . ."
Person 1: "Whoa! All Pencils Down! The beach is our ONLY summer break destination."