A fall arrest device having a safety support whilst allowing movement of the device on an elongate support. The fall arrest device including, a sliding element, first and second cam elements, first and second links, and an attachment. The first and second links connected together to mutually rotate about a third axis separated from a first and second axes, and the attachment moving relative to the links, so that the first and second locking cams can be moved between their first and second positions by loads applied to the device through the attachment.