This article presents a cultural and critical study of ‘proportionality review’ as a legal knowledge format and practice. The setting for this study is German public law, and in particular a domain of German legal education that is rarely analyzed even in Germany: the classes and materials offered by Repetitoren. These are commercial providers that aim to prepare students for the all-important ‘First Juridical Examination’. In this setting, proportionality is presented as a principle that matters, a doctrine that works, and a technique that jurists – lawyers, judges, but especially also law students – can learn to perform. Sustaining the sense that proportionality ‘works’, however, itself requires work, in particular in the form of largely invisible background constraints on what can count as suitable problems and appropriate solutions. In these processes of making proportionality into a ‘doable’ technical instrument, the German legal-constitutional order as a whole is presented as a feasible, achievable project. The article looks at how proportionality's success is produced and experienced, and at what its status as a foundational, near-ideal legal instrument means for the character of the German constitutional and legal imagination.