A nut and an assembly including such a nut are described herein, wherein the nut includes an outer shell having an outer surface, an inner circumferential surface having a inwardly extending flange, and an upper rim portion; and an insert piece having an upper outwardly extending portion and a plurality of downwardly extending projections, wherein each of the projections has an outer surface and an inner surface, a portion of the inner surfaces of the projections is configured to engage a nut-receiving surface and the outer portion of the projections is configured to engage the inner circumferential surface of the first outer shell such that upon a pushing action of a user the inwardly extending flange on the outer shell presses upwardly on the upper outwardly extending portion of the insert piece so that the portion of the inner surfaces of the projections configured to receive a nut-receiving surface moves outwardly and upon removal of the pushing action, portion of the inner surfaces of the projections configured to receive a nut-receiving surface moves inwardly.