Modification behaviors of forms created from model lines or forms created from reference lines will differ.
The following table specifies the differences between the two:
| Unconstrained form | Reference-based form |
|---|---|
Profiles created with any tool in the Draw panel using  (Model Line). |
Profiles created with any tool in the Draw panel using  (Reference Line), reference points, or any part of another form. |
Displays a solid line when highlighted.  |
Displays dashed reference planes around the line.  |
| Created when there is no need to rely on another form or type of reference. | Created when there is a need for a parametric relationship between the form and other geometry or references. |
| Not dependent on other objects. | Dependent on its references. When its dependent reference changes, the reference-based form changes. |
| Profiles are unlocked by default. | Profiles are locked by default for extrusions and sweeps. |
| The edges, surfaces, and vertices can be edited directly. | Edited by directly editing the reference element. For example, select a reference line and drag it using the 3D controls. |
| To convert lines to reference-based, select the Is Reference Line property under Identity Data on the Properties palette. | To convert lines to unconstrained, clear the Is Reference Line property under Identity Data on the Properties palette. |