What is "king post"

n. A central vertical supporting post used in architecture and bridge as well as in aircraft and ship design.

n. post connecting the crossbeam to the apex of a triangular truss

A king post (or king-post or kingpost) is a central vertical post used in architectural or bridge designs, working in tension to support a beam below from a truss apex above (whereas a crown post visually similar, supports items above from the beam below).

In aircraft design a strut called a king post acts in compression, similarly to an architectural crown post. Usage in mechanical plant and marine engineering differs again, as noted below.