Formwork is often made out of temporary moulds that hold the shape of the concrete until it hardens. Falsework refers to temporary structures, such as props or scaffolding, used to support arching or spanning structures until they can sustain themselves. The word "false" comes from the French for "falses", which means "for false"; thus, falsework is material used in construction to provide unsupported spans or arches. Temporary formwork is used in building projects where flexibility and speed are important. It allows the builder to make changes without having to start over from scratch. Examples include forming a base for a garden pond or creating forms for a concrete driveway. The moulds used for temporary formwork can be removed after a few hours or days and replaced with different shapes or templates if needed. People sometimes think of formwork as something permanent, but this is not the case. Forms are only used while the concrete is soft, usually when it's first placed in the trench and again before it sets up. Once the second pour is done, the original forms are pulled out and new ones put in their place. The term "falsework" is used instead because these structures are designed to be taken down once their purpose has been met. For example, a scaffold would be considered falsework because it is built for viewing a work site but then taken down after the job is done.