As further shown in FIG. 3B, substrate tiles 110 are held in X and Y position, for example and without limitation, with respect to adjacent ones of substrate tiles 110 so that probe tips 122 are held in X and Y registration in test plane 218, and substrate tiles 110 are aligned so that probe tips 122 thereon are substantially coplanar to test plane 218 (i.e., to a portion of test plane 218 to whic