A quick-mountable nut, which is capable of at least partially rotation-free axial displacement relative to a threaded bolt (22; 52), includes a nut housing (2; 45), and a springy holding member (4; 49) at least partially located in the nut housing (2; 45) and engaging in at least one screw thread (24; 54) of the threaded bolt (22, 52), with the central through-opening (3; 47) of the nut housing being formed as a tapering radially inward, inner cone (9; 48) for receiving the holding member (4; 49), and with the holding member (4; 49) having two, resiliently movable relative to each other, holding sections (5.1, 5.2; 50.1, 50.2) having each an even wall section abutting a wall of the inner cone (9, 48).