This chapter explains how constitutional interpretation, originalist or otherwise, does not always produce unambiguous rules of law that can be applied to cases. The Constitution requires more than originalist interpretation to be applied to cases and controversies. When interpretation has provided all the guidance it can but more guidance is needed, constitutional interpretation must be supplemented by constitutional construction—within the bounds established by original meaning. The chapter first considers the importance of construction to constitutional legitimacy before showing how construction fills the unavoidable gaps in constitutional meaning when interpretation has reached it limits. It argues that it is necessary to “construe” the Constitution in ways that effectuate its purposes but that do not contradict its original meaning. Constitutional constructions that are consistent with original meaning should be chosen to enhance the legitimacy of the laws that are going to be imposed on the people without their consent.