This document discusses different types of formwork and centering used in bridge construction. It describes centering for arches, including factors to consider like arch shape, span and thickness. Big arches may use timber truss, trestle or steel truss centering. Falsework supports arch structures during construction and consists of foundation pads, corbels, beams and posts. Slip formwork is an economical system for vertical structures like piers using sheathing, wales, yokes and scaffolds that eliminates joints and allows speedy construction.