Sections sketched on a part must be dimensioned for size and relative placement on the part. For dimensioning, the sketching plane does not have to be parallel to the screen—the part can be in any orientation. In fact, sometimes dimensioning the section with the model in a 3-D view helps avoid invalid dimensioning.
When sketching on a part, you can create these dimension types using these dimension tools:
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Normal—Create a dimension that references sketched entities only, or between a sketched entity and part geometry. These dimensions are used to solve the section and eventually become regular part dimensions.
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Perimeter—Dimensions the perimeter of the selected geometry.
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Baseline—Establish a baseline for ordinate dimensioning.
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Reference—Appear on a sketch for information only. Therefore, they are read-only and cannot be used to modify the model; however, they are automatically updated during regeneration if changes are made to the model.