The reference point is an auxiliary point positioned at one of the 4 points of the main part, and may be shown in a drawing as 
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The reference point is used as an additional dimensioned point in generation of some dimensions (for example, absolute dimensions). It is positioned on one of the ends of the main part's edge parallel to its axis (by default, the Bottom, Left point).
Position, size, and color of the reference point can be configured in the Reference point dialog,which opens when you click Ref. point in the New dimensioning style dialog.
