Abstract: A system and method for constructing fixtures for holding physical parts for welding, checking, inspection, and other related activities is provided. The physical parts include parts of cars as may appear in an automotive plant. The optimum L-unit components are selected based on the contour of the part to be held, the principle locating points for the part, and the geometry of the various L-unit components. The principle locating points identify where on the part is a L-unit fixture to be placed. The program reads the part contour data and principle locating points data to construct the criteria by which to select the optimum L-unit components from a relational database. The program allows the user to preselect a L-unit component and then determine the other fixture components needed to adequately hold the part. Also provided for are multiple L-unit types including rest, pin, and clamp L-units, as well as combinations of the L-unit types.