A part is designed so that a plurality of parts each identical to the part are arranged in the same attitude in parallel with a part moving direction on a guide (40), and includes projections (10f5, 10f6) for pushing an abutment surface (10f7) provided on a preceding part placed on the guide, while maintaining the attitude of the preceding part, and an abutment surface (10f7) to be pushed by projections (10f5, 10f6) provided on a succeeding part placed on the guide. The projections and the abutment surface are provided in an area of the part, which area is selected to avoid an area required to have dimensional precision whereby it is possible to supply the part to an assembly process without causing damage to the area required to have dimensional precision.