Abstract: A moulding unit for a plant for blow-moulding plastic containers (2) from respective parisons (3) comprises: two half-moulds (17a, 17b), movable relative to each other between a position of opening and a position of closing at least one cavity (19) for blow-moulding a respective container (2); and a locking device (21) for locking the two half-moulds (17a, 17b) in the closed position, the locking device (21) comprising two first fastening elements (22, 28) which are moved to, and normally held in, a locked position by at least one elastic actuating element (30).