Yale law professor Akhil Reed Amar continues his course on America's Unwritten Constitution by examining how practice, not text, fills gaps the Constitution leaves open. He traces how the House settled at 435 members, how Congress holds power over the size of the Supreme Court (including FDR's failed court-packing plan), and why majority rule functions as the Constitution's unstated default, with attention to the filibuster and Senate Rule 22. Amar closes with four case studies in constitutional fit: the legislative veto and the independent counsel, both of which broke with text and ultimately failed, against the Saxby fix and independent agencies, which fit the constitutional structure and survived. He ends with a brief look at Potter Stewart and recess appointments. The lecture is organized by clear chapter breaks and works as a focused case study in how unwritten custom shapes American constitutional practice.