You evaluate it the same as normal the orientation plane symbol is just stating what direction to make the evaluation. In the example you have shown the bore parallel to 'A' could have 2 possible directions of parallelism converging/diverging or twist/rotate. By placing a direction plane parallel to Datum 'B' the bores are constrained to control converging/diverging, the perpendicular to datum 'B' controls the direction for twist/rotate.
I think the graphic for the perpendicular control is misleading and should show the control planes 90 deg to those drawn.
You evaluate it the same as normal the orientation plane symbol is just stating what direction to make the evaluation. In the example you have shown the bore parallel to 'A' could have 2 possible directions of parallelism converging/diverging or twist/rotate. By placing a direction plane parallel to Datum 'B' the bores are constrained to control converging/diverging, the perpendicular to datum 'B' controls the direction for twist/rotate.
I think the graphic for the perpendicular control is misleading and should show the control planes 90 deg to those drawn.
