An extract from a school maths mechanics textbook reads:
To deal with cases in which the body is not rotating freely under gravity, we need to take into account also the work done by other external forces acting on the body. Suppose that $F$ is one such force, and let $OA$ be the perpendicular from the fixed axis to the line of action of $F$. By the principle of transmissibility we can take $A$ as the point of application of $F$.
Why is this case? This is a chapter on rotation about a fixed axis, following on from Moments of Inertia. Seeing as I previous been considering a body as a collection of masses, each with a force acting on them or their own energy, it seems odd to make this generalisation.
I have never encountered 'transmissibility' before so it is a foreign concept to me.