"demarcation lines" is a correct, usable phrase in written English.
You can use it to refer to a boundary or division between two or more things. For example: "The demarcation lines between the two warring countries were established by an international treaty."
There are no rigid demarcation lines.
These issues transcend the traditional demarcation lines.
The old demarcation lines are now largely inappropriate.
Buying them was my own take on the strangeness of existing property demarcation lines.
THE OLD DEMARCATION lines that have long defined Judaism are becoming obsolete.
On maps, demarcation lines can be moved, roads pencilled in, clear lines of fire drawn.
They might rather be called demarcation lines since they were clearly not intended as barriers to passage.
The demarcation lines that separate the modes of solid phase exothermic reactions were defined on the parametric diagram: Todes parameter – Semenov parameter.
The lines described in articles V and VI of this Agreement shall be designated as the Armistice Demarcation Lines and are delineated in pursuance of the purpose and intent of the resolution of the Security Council of 16 November 1948.
3. Rules and regulations of the armed forces of the Parties, which prohibit civilians from crossing the fighting lines or entering the area between the lines, shall remain in effect after the signing of this Agreement with application to the Armistice Demarcation Lines defined in articles V and VI.
Except where otherwise provided, the Armistice Demarcation Lines shall be established, including such withdrawal of forces as may be necessary for this purpose, within ten days from the date on which this Agreement is signed.
