A mine roof support has a goaf shield with a lemniscate guide system linking the shield to floor-engaging skids. A walking-mechanism is disposed in a channel between the floor skids. In order to prevent rubble or goaf material from penetrating into the channel the guides of the lemniscate system have connections which are spaced one above the other and to which one or several screen plates can be removably and replaceably attached with the aid of push-in locking-bars. The screen plates also advantageously serve to keep the floor skids apart by a minimum distance to prevent jamming of the walking mechanism.