If the target over which the instrument is to be placed is roughly at the same elevation as the tripod feet, the preceding technique is applicable. If there is a considerable difference between the elevation of the target and the elevation of the marker and the instrument bottom plate, such as when the target is in a deep hole, or on a Bilby tower, the target will appear to move laterally by a large distance in the optical plummet as the tribrach level is adjusted.