An analysis of all the falsework failures brought to notice of the Committee indicates that there is no single cause of collapse. Indeed, the cause are varied and widespread. In each case, however, one may discern the direct technical reasons for failure and also the contributory procedural failures which allowed the technical faults to go undetected. The purpose of most falsework is to support loads or to take reactions which are vertical. The forces in the horizontal plane are relatively small and difficult to quantify, so they tend to be inadequately allowed for. Lateral instability, and to a lesser extent longitudinal instability, are among the prime causes of failure. The fault in falsework design that occurs most commonly seems to be a neglect of horizontal forces and a failure to make provision for adequate lateral and longitudinal stability. Horizontal forces may be introduced by wind, vehicle braking, impact of buckets or vehicles, attempts to free stressing cables, guys, concrete placing methods or the use of form vibrators which can transmit compressive waves to the outermost members of the falsework. Internal vibrators, which have a direct effect on the concrete, impose fewer stresses on the substructure. The effects of crossfall of mudsills are particularly important. The downwards slope causes drainage towards the lower level with consequent ground weakening and differential settlement. Taller struts must be used on the lower side; these , when worker, deflect more, causing relative movement. a deeper filing of subgrade material will often slow more movement of the sole plate. Falsework constructed from the most carefully manufactured, properly selected and well maintained materials can be no safer than the expertise employed during erection. Although high standards of workmanship are not uncommon, there are examples, particularly on medium and small building operations, of poor standards. Examples of errors are: absence of effective bracing and lacing; eccentric loading in U-heads; and failure to reinforce around vehicular openings among others.