Blade of pd instrument should be.. perpindicular to shank

Blade of pd instrument should be:
A- perpindicular to long acsses .
B- parallel to long acsses.
C- perpindicular to shank.

A perpendicular designates two straight lines that intersect at an angle of 90 °.

Draw a perpendicular:
One method is to use a square. A square is an intrument in the shape of a right triangle. We place one of the short sides along the right D. We slide the square until the second small side meets the point M. This method has restrictions:
- You must have a square, and hold it well;
- On the sheet of paper, it must be supposed that the point M is close enough to D;
It is possible to draw a perpendicular to a line D passing through a point M without square. We use a ruler and a compass. We follow the following steps:
- With a compass, draw an arc of circle of center M which cuts D in two points (It is represented in red on the figure.). Note these two points A and B.
- Always with the compass, draw two arcs of centers A and B passing through M. (They are represented in green on the figure.) These two circles intersect in M, and the second point is noted N.
- The line linking M to N forms the perpendicular to D.