Note:  Do not rely on this information. It is very old.

Force-polygon

Force-polygon, in graphical statics, means a polygon drawn to scale such that its sides, taken concurrently, represent a set of forces in magnitude, direction, and sense. The forces being in equilibrium, it will be found that the polygon so drawn will be closed, i.e. the application of the last line to the figure, representing the last force in magnitude, direction, and sense, will completely close the figure. If the figure remains open, the forces will not be in equilibrium, but on addition to the system of a force represented to the same scale by the line joining the last point of the diagram to the first, balance may be made to obtain.