7-6-4

[sj]

I can see it may have been described poorly. I think I even confused myself but here's what was meant.

(a) parallel to and facing the line

A3
_______________

A1 A2 ^

with A1 and A2 looking in the direction of the arrow.


(b) Still parallel but facing perpendicular to the line:

A3
_____________

A1 A2 >

with A1 and A2 looking in the direction of the arrow,

Then there's the stack....

A3
_______________

A1
A2