Fall restraint may consist of a mobile scaffold or scissor hoist, provided that it extends for at least 2.0 meters on either side of a line directly up the slope of the roof to where persons are working. It must also sustain the additional overturning moments of a person sliding down a roof onto it, which may rule out lighter scaffolds and scissor hoists unless ties or additional stability is provided. Care must be taken to ensure that such mobile scaffolds are constantly moved as work progresses.