Abstract: A walking mine-roof support comprising two roof support units which are to be moved with respect to one another for advancing the support, each of the units including a pair of spaced-apart frames each comprising a pair of hydraulically-extensible props disposed one at each side of the frame connected to a cross-member extending between the props, the two frames of each unit being interconnected by roof-supporting bars connected to the cross-members of the frames, the two roof support units overlapping one another in the direction of advance of the support so that first and third frames form a leading one of the units and second and fourth frames form the other unit which is a trailing unit, the two frames of one unit being connected to a frame of the other unit disposed between the two frames by respective first and second rams, whereby during relative movement between the units one of the rams is extended while the other retracts.