A safety unit comprising: a support structure of two or more vertical members; a barrier extending between, and demountably supported by way of, at least two of the vertical members; a foot plate for each vertical member by means of which the vertical member is mounted on a supporting surface; at least one engagement means whereby the foot plate can resist sliding relative to the supporting surface or an extension thereof; a traveller slidably mounted on the vertical member, the traveller being adapted for displacement along a longitudinal axis of the vertical member and for rotation about the vertical axis; the traveller including a clamp whereby the traveller can be secured against displacement along the longitudinal axis and rotation about the vertical axis; at least one prop having a first and a second end; the first end being pivotably attached to the traveller; the second end being adapted for location on and engagement with the supporting surface; and a link having a first and a second end; the first end of the link being pivotably attached to the prop intermediate the first and second ends of the prop; the second end of the prop being pivotably attached to a slider on the vertical member at a point intermediate the traveller and the foot plate; the slider being adapted to rotate about the vertical axis of the vertical member.
