steel
Pretty much all of it. The neck, head and body have to be able to handle the tension of the strings. The faceboard has the bridge and that is heavily stressed by the strings.
Bridge is a noun.
The word bridge is a noun. The plural form is bridges.
stone
beam
A covered bridge is a timer-truss bridge. The bridge has a roof and siding which covers almost all parts of the bridge. Some famous covered bridges are the Buchfart bridge and the Hartland Bridge.
A bridge is a frame structure because it is made out of parts that are fastened together
What the answer
Compression
The Ben Franklin Bridge connects Pennsylvania and New Jersey. Parts of the bridge are thus in one state or the other.
Is the belt routed correctly? your local auto parts store could help with routing diagrams.
bridge and main deck