The phrase "demarcation line" refers to a boundary or line that separates two areas or territories. It is used to clearly define and distinguish where one area ends and another begins. Full definition
At this point, as a Management Consultant who grew up in a world where there was a clear demarcation line between consultants and professional services and the world of hardware and software, I realized that my world had changed. (slaw.ca)
North Korean leader Kim Jong Un and South Korean President Moon Jae - in walk across the military demarcation line ahead of the inter-Korean summit (nigeriapoliticsonline.com)
Matthew Oakeshott, the Liberal Democrat treasury spokesman, said there needed to be clear demarcation lines between the governor and parliament to maintain the Bank's independence. (macleans.ca)