We describe the development of measures of teachers' recognition of an instructional norm--that proof problems in high school geometry are presented in a diagrammatic register. A first instrument required participants to openly respond to depictions of classroom scenarios in which the norm was breached. A second instrument was a survey that required participants to rate the extent to which they agreed with various explicit statements about instruction. A third instrument capitalized on pros of the other two. We demonstrate how this instrument development process improved our conceptualization of the components included in the diagrammatic register norm. [For the complete proceedings, see ED584443.]