i. Direct shear (or simple shear) in which the shear stresses are created by the direct action of the forces in trying to cut through the material

ii. Shear stresses also arise in an indirect manner when members are subjected to tension, torsion, and bending

Equality of Shear Stresses on Perpendicular Planes

i. Shear stresses on opposite (and parallel) faces of an element are equal in magnitude and opposite in direction.

ii. Shear stresses on adjacent (and perpendicular) faces of an element are equal in magnitude and have directions such that either stresses point toward, or both point away from, the line of intersection of the faces.