Which are properties of liquid crystals

The situation is not shown, however if one calculates torques about the pivot point, then the pivot point itself exerts no torque because the force applied by the pivot point exerts zero torque because Fp * L = 0 where L = 0 in this case.

If one wants to calculate torques about, say, the end of the ruler then one would need to calculate the torque applied by the pivot point.