Top and bottom lateral bracing and portal bracing, sway bracing and struts are secondary members which help to stiffen the structure. The deck is the surface on which traffic or pedestrians ride or walk. The traditional truss type with its origins in the middle ages. A king post truss is the simplest form of a truss bridge. This type has a bottom chord and two diagonal members meeting at the center of the structure.
Some variations have vertical posts or diagonals.
The peak of the King Post is replaced by a horizontal top chord. This allows for bridges with longer spans. Multiple King Post Truss is series of King Posts trusses symetrical about the center of the bridge. Bridge spans are longer than that of the King Post. A Town Lattice Truss is a system of timber diagonals with no verticals.