Let us take an example: A block $\backslash (100\backslash$mathrm$\{$~mm$\}\backslash$times $100\backslash$mathrm$\{$~mm$\}\backslash )$ base and $10$ mm height. When we apply a tangential force $10$ kN to the upper edge it is displaced $1$ mm relative to lower face.

Then the direct shear stress in the element