Lesson seven of a course on holding the model while an AI does the work. The gauge is the machinist’s go/no-go gauge, and the rule is Kent Beck’s (Test-Driven Development: By Example, 2002): write the check before the code, because once the output exists it argues for itself: a finished-looking part moves the line for what passes. The two questions are not a quiz; committing before the drawing resolves is what makes it stick.