Provided herein in some embodiments is an instrument including an annular body, a plurality of caliper-tip pairs, and a plurality of through holes. The annular body includes an inner perimeter portion, an outer perimeter portion, and a medial portion in-between the inner perimeter portion and the outer perimeter portion. The plurality of caliper-tip pairs are disposed about the outer perimeter portion of the annular body, wherein each caliper-tip pair of the plurality of caliper-tip pairs has a different fixed caliper-tip spacing. The plurality of through holes are disposed about the medial portion of the annular body in pairs, wherein each pair of through holes of the plurality of through holes has a through-hole spacing matching the fixed caliper-tip spacing of at least one caliper-tip pair of the plurality of caliper-tip pairs.
