Dimensioning was the first new feature installed in AutoCAD after COMDEX 1982, and the first deliberately intended as an extra cost add-on. The complete design of the initial dimensioning facility is presented here as an example of the developer documentation of the period. This very crude first cut at dimensioning became the entire content of the ``Advanced Drafting Extension'' (then called, ``with Dimensioning'') offered as a $500 option with AutoCAD 1.2 in April 1982.