Lesbian rule

noun2

1. •
   (rare) A flexible leaden mason's rule that can be bent around the curves of a molding, and thus used to measure or reproduce irregular curves.

   • Or, with a Lesbian rule—that strip of soft lead which could be pressed into a particularly satisfying molding to record its profile—we explored buildings that interested us. — 1957
2. •
   A flexible principle, one which may be bent to accommodate or fit different circumstances.

   • He asks: “Is Scripture become a Lesbian rule and bowed to our fancies? But this is the very answer that a classical brother gave me […] — 1850