Assembly formed by assembling two parts (1, 2), in particular of a bodywork, of a motor vehicle comprising: - a first part; - a second part, said first and second parts (1, 2) being assembled by clipping or snap-fitting; - a locking element intended to prevent any relative displacement between the first and second parts (1, 2), said locking element being able to be displaced in rotation about an axis (ZZ') under the action of maneuvering means between an unlocked position, in which a relative displacement between the first and second parts (1, 2) is possible, and a locked position, in which it prevents any relative displacement between the first and second parts (1, 2), characterized in that the locking element comprises: - a substantially cylindrical body which is centered on the axis (ZZ'), said body being partially housed inside a circular arc shaped cavity formed in a planar portion of the second part, said planar portion being aligned in a plane which is perpendicular to the axis (ZZ'); - a pair of retaining fins (42, 43), each of the retaining fins (42, 43) comprising an upper edge (421, 431) extending radially from a peripheral surface of said body and a lateral edge (422, 432) extending coaxially to said peripheral surface, one of the retaining fins forming with the body an annular groove configured such that, in the locked position of the locking element, it allows housing at least partially a retaining element of the first part and another of the retaining fins forming, with the body, an annular groove which is configured such that, in the locked position of the locking element, it allows housing at least partially a retaining element of the second part, said retaining elements (124, 224) having at least partially a profile which is substantially complementary to that of said annular grooves (44, 45), and that, in the unlocked position of the locking element, said retaining elements (124, 224) are disposed outside said annular grooves (44, 45); and in that at least one of the first and second parts (1, 2) comprises a stop element which is configured such that, in the locked position of the locking element, it prevents any axial displacement of the locking element relative to the first and second parts (1, 2). - a first part; - a second part, said first and second parts (1, 2) being assembled by clipping or snap-fitting; - a locking element intended to prevent any relative displacement between the first and second parts (1, 2), said locking element being able to be displaced in rotation about an axis (ZZ') under the action of maneuvering means between an unlocked position, in which a relative displacement between the first and second parts (1, 2) is possible, and a locked position, in which it prevents any relative displacement between the first and second parts (1, 2), - a substantially cylindrical body which is centered on the axis (ZZ'), said body being partially housed inside a circular arc shaped cavity formed in a planar portion of the second part, said planar portion being aligned in a plane which is perpendicular to the axis (ZZ'); - a pair of retaining fins (42, 43), each of the retaining fins (42, 43) comprising an upper edge (421, 431) extending radially from a peripheral surface of said body and a lateral edge (422, 432) extending coaxially to said peripheral surface, one of the retaining fins forming with the body an annular groove configured such that, in the locked position of the locking element, it allows housing at least partially a retaining element of the first part and another of the retaining fins forming, with the body, an annular groove which is configured such that, in the locked position of the locking element, it allows housing at least partially a retaining element of the second part, said retaining elements (124, 224) having at least partially a profile which is substantially complementary to that of said annular grooves (44, 45), and that, in the unlocked position of the locking element, said retaining elements (124, 224) are disposed outside said annular grooves (44, 45); and