A fastener has a head for retaining a vehicle component and a leg to be fitted into a mounting hole of a panel. The leg has a plurality of resilient engaging walls extending in the axis directLon with a plurality of vertical slits interposed therebetween. Upper ends of the walls are connected to the head and lower ends of the walls are connected to one another. Each upper end connected to the head is provided with a lateral cut. The presence of the cut makes the wall to easily flex inwardly when the leg is inserted into the mounting hole of the panel, enabling the insertion of the leg with smaller force, resulting in significant improvement in workability.