Wall fails to form using closed dwire

[damian]

Should that 'last point before start be 0,7.33,0? (rather than -8yd, 0,0 or 0,0,0)

No
If your 'Start' is (0,0,0) the 'End' is (-8,0,0), following the @Dgingrey's instructions.
Another question is that @Dgingrey includes two edges over the same line, one began at (0,0,0) and other began at (-8,0,0)

I do not quite remember where I might have read the FC 'right hand' rule?

The 'right hand' rule is not an FC rule. It's a universal rule, used in geometry, physic, etc. You can read about it in https://en.wikipedia.org/wiki/Right-hand_rule.
The other 'rule' or criteria is a more specialized concept, owner of a few programs, and again it isn't an FC concept. It consists in to start your draw by the vertex with the less Y coordinate, and when there are two o more vertices with this Y coordinate (low), to select the one of them with the less X coordinate (left). The second part is to ubicate this lower left point at the origin of the coordinates (0,0,0). Nothing in FreeCAD force to you to follow this rule, but generally, it's a good strategy to improve the user orientation and sometimes avoid problems.

[Dgingrey]

The direction of rotation when forming the dwire does indeed seem to be affecting the results. When I construct the same dwire starting at the origin (0,0,0) and ending at the origin (0,0,0) but drawing in a clockwise rotation the wall forms correctly. Experimenting further I found that if the
first segment of the dwire is parallel to the x-axis and the closing segment is also parallel to the x-axis and the dwire has been constructed in a counter clockwise direction then the wall fails. If the beginning segment and the closing segment are parallel to the y-axis or the beginning segment
and closing segment are perpendicular to each other then it doesn't matter which direction, clockwise or counter clockwise, you draw the dwire, the
wall forms correctly.

[damian]

The direction of rotation when forming the dwire does indeed seem to be affecting the results. When I construct the same dwire starting at the origin (0,0,0) and ending at the origin (0,0,0) but drawing in a clockwise rotation the wall forms correctly.

yes

Experimenting further I found that if the
first segment of the dwire is parallel to the x-axis and the closing segment is also parallel to the x-axis and the dwire has been constructed in a counter clockwise direction then the wall fails. If the beginning segment and the closing segment are parallel to the y-axis or the beginning segment
and closing segment are perpendicular to each other then it doesn't matter which direction, clockwise or counter clockwise, you draw the dwire, the
wall forms correctly.

yes

[paullee]

Thanks Damian for the explanation of the Right Hand Rule etc.

I remember the Right Hand Rule for physics but does not aware the implication in drafting wire

The direction of rotation when forming the dwire does indeed seem to be affecting the results. When I construct the same dwire starting at the origin (0,0,0) and ending at the origin (0,0,0) but drawing in a clockwise rotation the wall forms correctly.

yes

I thought Right Hand Rule means drawings Counter-clockwise better?

Experimenting further I found that if the
first segment of the dwire is parallel to the x-axis and the closing segment is also parallel to the x-axis and the dwire has been constructed in a counter clockwise direction then the wall fails. If the beginning segment and the closing segment are parallel to the y-axis or the beginning segment
and closing segment are perpendicular to each other then it doesn't matter which direction, clockwise or counter clockwise, you draw the dwire, the
wall forms correctly.

Or should afterall - do not draw the 'Last' Segment but just let Dwire 'close' it for you better?