Principle of transmissibility
Principle of transmissibility: If a force is acting at a point on a body then it is assumed that the point of application of a force can be transmitted anywhere on its line of action within the body (without disturbing its condition of equilibrium). Following figure shows the force F is acting at a point 'A' on the body and the new position is represented at point 'B' on the same line of action, within the body.