Roman Muñoz wrote:
OK, now I get the arrow, but there are problems: section line is missing from first point to second: only begin of line and entire arrow is shown, or sometimes, part of perpendicular line is visible, but then it's on the passage. I think I'm missing something, but I can't figure what it is.
You have probably misplaced the control points -- they determine how long segments will be drawn. See the attached picture which displays their correct position.
I guess there is a good reason to do it with a curve instead of a segment, but it's a pity, because the segment is much more handier.
You may draw a segment either, but you get solid line crossing the passage. Drawing a curve makes it possible to control the omitted part in the middle. Even if you draw a curve, displayed will be straight segments, not a curve. Regards, Martin