Abstract: A roof support has a pair of floor sills carrying hydraulic props supporting a roof-engaging structure. The floor sills have guide rails on their adjacent sides which mate with a slidable guide block which connects to a shifting ram and thrust mechanism between the sills. The shifting ram has one of its displaceable parts, i.e. its cylinder or piston rod articulated to a thrust beam or a pair of thrust rods which link with a conveyor in front of the support. The sills are interconnected for relative vertical movement and are coupled to the other displaceable part of the ram. The guide is linked to the thrust beam or thrust rods remote from the conveyor by way of a pivot joint which resists traction but permits pivoting about an axis generally parallel to the ram and which is easily assembled and dismounted.