Creo Simulate > References > Sketcher > Dimensioning Sketcher Geometry > Working with Dimension Tools > Reference Dimensions > To Create Reference Dimensions
  
To Create Reference Dimensions
Use the reference dimension tool to create a new reference dimension, or use the shortcut menu or the Sketch menu to convert a normal dimension to a reference dimension.
To Create a New Reference Dimension
1. Click Sketch > Reference and select the entities to define the dimension.
2. Middle-click to place the dimension. The reference dimension is created.
To Convert a Normal Dimension to a Reference Dimension
1. Select the dimension to convert.
2. Right-click and choose Reference from the shortcut menu or click Sketch > Operations > Convert To > Reference. The dimension is converted.