A grommet (200, 300, 400), a stud (102), an assembly of a grommet and a stud forming a fastener (100), and a method of assembling a grommet and a stud to form a fastener has the grommet with an interengaging element (250) in a channel wall of the grommet for engaging a cooperating, compatible or complementary interengaging element in a wall of the stud. The grommet and the stud can be assembled by moving the grommet and the stud relative to each other until the interengaging element in the grommet engages the complementary interengaging element in the stud. A family of grommets is described.