Clearances and profiles must be respected to very tight tolerances on car assembly lines. Thanks to discussions with the production technicians, we devised and built a test jig using 3D printing techniques (in compliance with our concept to reality motto). The jig makes it possible to establish whether the profile of a headlight bezel is perfectly identical to the theoretical surface profile. With a fast positioning operation and quick visual check, the operator can install conforming parts and discard any off-spec pieces.