An exercise in finding the ‘perfect box,’ this drawing is a heuristic device developed to analyze a set of seminal architectural projects. The plans of Mies van der Rohe’s clear-span structures are overlaid about a common corner, revealing similarities and differences in size, proportion, and meter. The dimensions of the building modules are then averaged. These projects exhibit Mies’ notion of the Modernist ideal of Universal Space: total and absolute horizontal spatial continuity. If Mies’ project was to find the ideal geometry for this idealized condition, averaging his various structural spans is an attempt to find that geometry on the architect’s own terms. The result is an average module, the basic building block of the ‘ideal’ box.