Abstract: A method and a positioning door jig for selecting a suitable coating door jig is disclosed. A coating door jig is temporarily connected between a door opening at a side of a vehicle body to be coated and a slide door so as to enable forward and rearward movement of the slide door. The coating door jig forms a constrained linkage for guiding the slide door along a predetermined locus. The coating door jig is selected depending on a kind of automobile to be coated by the use of a positioning door jig. The positioning door jig forms a non-constrained linkage comprising mechanismic elements same as those of the constrained linkage and another additional mechanismic element. After temporarily connecting the positioning door jig between the slide door and the door opening, the kinematic pair position connecting the additional mechanismic element and one of the said mechanismic elements is adjusted so as to specify relative positions of the respective mechanismic elements.