Roof support suitable for use in mines

A roof support suitable for use in mines including a roof-engageable member and a cantilever member, one of these two members comprising a base, a cover member providing a roof-engageable surface, and a plurality of longitudinal members secured, in parallel manner, both to said base and said cover member, whereby said base, cover member and longitudinal members together form a plurality of parallel elongate compartments extending in the lengthwise direction of the cover member, and the other of said two members including a plurality of parallel and rigid elongate elements slidably fitting into said compartments and joined together at least at their end portions remote from said one member, said other member also including a plate, having a roof-engageable surface, which defines the profile in plan of that member and which is so secured to said elements, in parallel relation therewith, as to be relatively slidable upon and with respect to said roof-engageable surface of said cover member, the transverse widths of said surfaces being such that when said roof-engageable member and said cantilever member are caused by actuator means relatively to slide from a retracted condition to an extended condition, or to a partially-extended condition, one of said roof-engageable surfaces effectively forms a full width extension of the other of said roof-engageable surfaces.