Other forms: trestles
A trestle is a special kind of tower built to support a bridge.
A "trestle bridge" will usually have a trestle on each side, and there might be more trestles if the bridge is particularly heavy or long. Engineers need to carefully design the trestles so they will hold up the bridge when it's full of traffic. Modern trestles are usually built of concrete or steel, while older ones are often wooden.