Clamping apparatus and apparatus for use in erecting temporary guard rails

An apparatus for use in clamping a structure at its edge, the structure having opposed surfaces, the apparatus comprising a stanchion, a first clamping assembly attached to the stanchion and a second clamping assembly selectively slidably moveable longitudinally along the stanchion, the second clamping assembly including a support plate extending laterally outward in a direction away from the stanchion, the support plate being positioned closely adjacent one of the opposed surfaces of the structure when the structure is clamped between the first and second clamping assemblies.