Which component of a 3-element Yagi antenna is primarily for mechanical support?

A standard 3-element Yagi antenna is made up of three active electrical parts: the driven element (which connects directly to the feedline), a reflector (placed behind the driven element), and a director (placed in front of the driven element). These three elements are responsible for radiating, receiving, and focusing the radio frequency (RF) energy into a directional beam. However, they need to be held rigidly in place at very specific distances from one another to function properly. The boom is the central structural pipe or rod running perpendicular to these elements. Its sole purpose is to mechanically support the elements and attach the entire antenna assembly to the mast.