An apparatus for mounting support tileframes for electrical devices includes a mechanism for holding the tileframe, inserted into the said tileframe or guided for holding by the user, two or more chucks, whose number varies according to the number of screws to be fixed on the tileframe, each of which is equipped with an insert for holding and directing the rotation of one of the screws, and in which the chucks are activated, simultaneously and in the same direction, either to screw tight or unscrew said screws, by means of a screwing attachment, which can be attached temporarily to the apparatus.