A disclosed jig, for use in certifying accuracy of a vehicle wheel aligner, includes two axles of equal length having stub shafts at the ends of the axles and two adjustable side spacers for releasable connection to the stub shafts. Plates for mounting heads of the aligner system also are attached to the stub shafts. Stands support the corners of the rectangular jig formed by the connected axles and spacers. The aligner system measures parameters of the jig from the attached heads. A diagonal spacer of a predetermined length, may be used in setting the diagonals of the rectangular jig during assembly to be equal. In the example disclosed, the apparatus also includes a distance setting shaft for use in setting lengths of each of the two side spacers to be equal.