Access. While a worker can theoretically approach a hanging scaffold from a ladder, the recommended industrial practice is to access the scaffold from a rooftop or the ground, and then raise or lower the scaffold to its working location. Rooftops are the most practical access point for small worksites, while the ground provides easy reach for large projects. There are two main types of scaffolding: horizontal and vertical. Horizontal scaffolding consists of boards that span between two structures at right angles to each other. The boards are usually made of wood, but metal frames with wooden planks attached are also used. Vertical scaffolding uses poles set in the ground or bolted to a framework's legs to support layers of boards or mesh. This type of scaffolding is useful for reaching high places or constructing temporary structures. Suspended scaffolding is a third type of scaffolding. Rather than being fixed to another structure, it is held up by ropes or wires tied to anchors fixed into the building itself. This type of scaffolding is used mainly for interior work where fixed scaffolding could interfere with passing equipment or pose a fall hazard. It is also used for high-level work where fixed scaffolding would be difficult or dangerous to use. The type of scaffolding used depends on the size of project, location of work, and personal preference.