The present invention concerns a protective cover for the sliding guides of a mobile machine tool part and comprises a set of rigid panels which overlap and are guided in such a way that they slide parallel with the machine tool guides, and panel pulling means, designed so that, when a first, driven panel is moved, they allow the subsequent panels in the set to be pulled. The pulling means comprise a pulling element, attached to the first panel, parallel with a direction transversal to the set of planes upon which the subsequent panels in the set lie; and contact faces, on the subsequent panels, opposite the pulling element. The contact faces are positioned in the path of the pulling element at different positions, longitudinal to the guides, so that each is intercepted by the pulling element at a different time as the element moves, thus allowing all of the subsequent panels in the set to be pulled.