Probing is a common operation employed to reduce the position uncertainty o
f objects. This paper demonstrates a technique for constructing provably ne
ar-optimal probing strategies for precisely localizing polygonal parts. Thi
s problem is shown to be dual to the well-studied grasping problem of compu
ting optimal finger placements as defined by B. Mishra and others. A useful
quality metric of any given probing strategy, can easily be computed from
simple geometric constructions in the displacement space of the polygon. Th
e approach will always find a minimal set of probes that is guaranteed to b
e near optimal for constraining the position of the polygon. The size of th
e resulting set of probes is within O (1) of the optimal number of probes a
nd can be computed in O (n log(2) n) time, whereas the exact optimal soluti
on is in NP-hard. The result of this work is a probing strategy useful in p
ractice for refining part poses.