F.O.B. can be used decoratively to visually link two distinct areas or to signal a transaction. Footbridges are often situated to allow pedestrians to cross water. They are also located across roads to let pedestrians cross safely without slowing down the traffic. Footbridges are small, but important, because they are usually presented in townscape. The appearance of footbridges, and indeed of any other bridges, in a town, is a major concern for designers. Footbridges can also be built in the same ways as road and rail bridges. Most footbridges are equipped with guard rails to reduce the risk of pedestrians falling.