Use the Constraint Set command to constrain two UCS together. The Constraint Set creates three flush constraints to the origin planes of each UCS, which fully constrains the two UCS.
You can select UCS in part or assembly environment.
To use Constrain to place UCS constraints
On the ribbon, click Assemble tab Relationships panel Constrain .
In the dialog box, click the Constraint Set tab.
Optionally, select the Pick Part First box.
Select the UCS to reposition. If necessary, click the First Selection to enable the selection.
Select the second UCS. If necessary, click Second Selection to enable the selection.
If Show Preview is selected, observe the effects of the applied constraint.
Click Apply to continue to place constraints or click OK to create the constraint and close the dialog box.
To use Assemble to place UCS constraints
On the ribbon, click Assemble tabRelationships panelAssemble .
Select the UCS to reposition.
Select the second UCS.
Do one of the following:
Click Apply and continue to place constraints.
Click OK to create the constraint and close the mini toolbar.
Click Undo to delete the selections and continue to place constraints.