No part of a constitution is more important than the rules that govern its amendment and its entrenchment against it. Given the important functions served by formal constitutional amendment rules, we might expect constitutional designers to entrench them against ordinary amendment, for instance by requiring a higher-than-usual quantum of agreement for their amendment or by making them altogether unamendable. Yet relatively few constitutional democracies set a higher threshold for formally amending formal amendment rules. In this Article, I demonstrate that existing written and unwritten limits to formally amending formal amendment rules are unsatisfactory, and I offer modest textual entrenchment strategies to insulate formal amendment rules...