boundary line; edge line; break line
Technical term used in design, drafting, and manufacturing to indicate a line where a part is cut, folded, or separated. Often seen in CAD, sewing patterns, and sheet metal work.
Please cut the material along the break line on this drawing.
Clearly draw the cutting line on the pattern.
Compound of 見切り (みきり, 'seeing and cutting off' or 'abandonment') + 線 (せん, 'line'). The exact derivation is uncertain; the term is conventionally used in technical fields for a cutting or separation line.