A recessed support, preferably in a recessed box, for hidden sockets, comprises a front face from which a recessed compartment extends which is destined to house electric plugs inserted in the sockets and which has an inclined lateral wall on which at least an electrical socket is afforded. A slidable cover is associated to the front face, which is constrained to the body of the support by guide and sliding means so as to be slidable between a closed position for covering the compartment and an open position which uncovers the compartment. Also present are a first and a second blocking screw of the socket to the inclined lateral wall; both the first and the second blocking screw in turn comprise: a stem having at least a threaded portion; a screwing head having a transversal dimension that is greater than the stem; the stem being interposed between the cover in the closed position and the head.