We catalogue here the conditions for which a 2-D void of a given configuration is geometrically allowable. If one or more of the conditions for a particular configuration is violated, then that configuration is disallowed even if it would have the minimum free energy.
If either of the first two constraints is not met, then the void is so large that only a span configuration is geometrically possible. If either the third or fourth condition is not met, then no portion of a circle can simultaneously meet the wall and base at the required contact angles.
