King post truss
A central post carries the ridge, struts walk the load down to the walls.
The king post is the oldest trick in the book: one vertical post at the peak, running from the ridge down to the tie beam, with two struts kicking the load out to the walls.
How it works
king post central, carries the ridge struts pair, walk the load down to the tie beam tie beam resists the roof's outward push span up to ~24 ft without center support
When to use it
Barns, chapels, and any room with a simple gable you want to keep light and open. The triangle is unbeatable for stiffness per pound of oak.