plumb rule
noun
a device for determining perpendicularity, consisting of a narrow board with a plumb line and bob suspended from an upper edge.
Origin of plumb rule
1350–1400; Middle English
plomreule
Words nearby plumb rule
plumate,
plumb,
plumb bob,
plumb joint,
plumb line,
plumb rule,
plumbaginaceous,
plumbaginous,
plumbago,
plumbeous,
plumber
British Dictionary definitions for plumb rule
plumb rule
noun
a plumb line attached to a narrow board, used by builders, surveyors, etc