Moving into the Assembly World - Autodesk Inventor 2010: No Experience Required - page 145

FIGURE 3.30 Moving a component into open space can make it easier to
apply assembly constraints.
11. The duct moves into position — but remember, it's only a preview.
Click the Apply button to create the constraint and keep the dialog
available for the next constraint.
12. Rotate your view so you can see the top edge of the face on the duct
(with the holes) and the top of the housing. Verify that the material
of the duct mounting faces aren't intersecting with the housing. See
Figure 3.31.
13. Switch the Constraint Type to Angle.
14. For the fi rst selection, pick the top of the housing, as shown in
Figure 3.31.
15. For the second selection, pick the thin top face of the duct, as shown
in Figure 3.31.
16. Leave the Angle value at 0, and click OK to create the constraint.
17. The two parts should look like Figure 3.32.