Abstract: Of those constituted by the association of a trencher comprising a cutting disc (2) with a prefabricated tongued and grooved element feeder comprising a sweeper box (32) with a U-shaped transversal section closed at the front by a rake (34), in such a way that earth cannot fall inside it, and means of pushing the prefabricated tongued and grooved elements (33) comprising drive wheels (7) which transmit to them, by friction, a longitudinal push in order to keep the different prefabricated tongued and grooved elements (33) coupled together during their descent into the inside of the sweeper box (32). This constitutes a kind of temporary plank mould for the trench, on account of which the lowering and laying of the prefabricated tongued and grooved elements (33) inside it may be carried out automatically, safely, and in a working environment that is free of earth, thus enabling the perfect linking of the elements.