A fixture set includes an accessory part, and at least one means for fixing the accessory part to a front surface of a wall of a hollow frame, through a hole provided through the wall. The fixing means includes an anchor, a bolt screwed into the anchor and a splitter arranged between the head of the bolt and the anchor. The anchor is entirely inserted in the hole and includes at least two parts which are radially expandable by the splitter, when tightening the bolt, to lock the anchor against the back surface of the wall. The splitter and the anchor include mutually interlockable structures for substantially restricting rotation of the anchor relative to the splitter. The accessory part, or an intermediate accessory piece arranged between the accessory part and the wall, includes a solid connection for substantially restricting rotation of the splitter relative to the accessory part.