A special mounting holder for fixing flush mounted junction boxes in a wall chase. In a prepared chase, the boxes, which are connected serially and equipped with holders, are nailed to the wall. This guarantees their even embedding before the plastering process. Such mounting facilitates and accelerates the work, ensuring the precision of box embedding. While ordering, it is necessary to note that each box requires two holders. The product is suitable for mounting elements used in the body of serial boxes with membrane knockouts and boxes E106-2K, E107-2K.