A clip comprising: a pin having at at least a part thereof a noncircular cross-section and a grommet having an insertion hole into which the pin can be inserted, a part of the grommet being partly expandable by insertion of the pin into the insertion hole, wherein the pin includes a head member, an axis member having an approximate circular cross-section below the head member which is formed integrally with the head member, and a rib protruding from a part of the axis member, which acts to effect temporary or permanent fixing of said pin, wherein the grommet has a ramp provided at an entrance hole edge of the insertion hole and leading the pin into the insertion hole when the pin is displaced from a normal position and contacts the entrance hole edge of the insertion hole, and characterized in that the ramp is configured such that, when the pin and the grommet are subjected to a stress in a direction approaching each other, the pin or the grommet is rotated around a center axis of the other member after the rib comes into contact with said ramp, wherein the grommet includes an approximately tubular leg member forming the insertion hole, a flange member circularly protruding from an upper outer periphery of said leg member, and a plurality of slits disposed in the leg member and extending from a tip of said leg member to a bottom surface area of the flange, said pin being temporarily fixed when the rib fits in the slits, and wherein the ramp is disposed in the entrance hole edge of the insertion hole, is located at an upper portion of each leg piece defined between the slits and forming the leg member, and inclines from a position corresponding to an approximate intermediate portion between adjacent slits located on both sides of the leg piece toward the slits on both sides, or from a position corresponding to either of the slits located on both sides of the leg piece toward the other. a pin having at at least a part thereof a noncircular cross-section and a grommet having an insertion hole into which the pin can be inserted, a part of the grommet being partly expandable by insertion of the pin into the insertion hole, wherein the pin includes a head member, an axis member having an approximate circular cross-section below the head member which is formed integrally with the head member, and a rib protruding from a part of the axis member, which acts to effect temporary or permanent fixing of said pin, wherein the grommet has a ramp provided at an entrance hole edge of the insertion hole and leading the pin into the insertion hole when the pin is displaced from a normal position and contacts the entrance hole edge of the insertion hole, and characterized in that the ramp is configured such that, when the pin and the grommet are subjected to a stress in a direction approaching each other, the pin or the grommet is rotated around a center axis of the other member after the rib comes into contact with said ramp, wherein the grommet includes an approximately tubular leg member forming the insertion hole, a flange member circularly protruding from an upper outer periphery of said leg member, and a plurality of slits disposed in the leg member and extending from a tip of said leg member to a bottom surface area of the flange, said pin being temporarily fixed when the rib fits in the slits, and wherein the ramp is disposed in the entrance hole edge of the insertion hole, is located at an upper portion of each leg piece defined between the slits and forming the leg member, and inclines from a position corresponding to an approximate intermediate portion between adjacent slits located on both sides of the leg piece toward the slits on both sides, or from a position corresponding to either of the slits located on both sides of the leg piece toward the other.