PCB gerbers board edge line is 0.254mm wide

[cupoftea]

Supposing in your PCB and gerbers, your board edge line is 0.254mm wide (thick). Will the PCB manufacturer take it that the actual “edge” is in the middle of the line?

 

[ZASto]

You should ask your preferred manufacturer.

 

[FvM]

Will the PCB manufacturer take it that the actual “edge” is in the middle of the line?

That's the usual interpretation of contur lines. If you are unsure, why don't you reduce the aperture?

 

[dick_freebird]

It's probably a zero width target line with +/- 5 mils tolerance
for the saw kerf / shear / whatever singulates boards
from the panel, if this measurement is at the panel level.

But if it's incorporated in a single board's extents this could
be a "half-scribe", making a 20 mil lane when butted (CL
+/- 10 mils tolerance).

PCB house ought to have some "how we build a panel for
fabrication" docs that tell you what's what, you'd think.