Line - can be center of circular edge selected edge work axis Normal A vector perpendicular to an outside face on a part. These are used to specify exact constraints. Constraints come in four types. They can be planes, lines or points. Flush causes two planes to be level with one another and their normals pointing in the same direction.
Angle orients two planes at the specified angle to one another.
When parts are inserted, they are completely free to move about. The only exception to this is the first part inserted. This is called the base or grounded component. It has zero degrees of freedom, ie. Be careful tochoose an appropriate part as the grounded component.