Mates in Multibody Parts
In multibody parts, you can precisely place bodies using mates. The
following mates are supported:
Angle
Coincident
Concentric
Distance
Parallel
Perpendicular
Tangent
When you insert a part into an existing part
file, mate references in the inserted part are used automatically to place
the inserted part. A preview shows the application of the mate reference
as you insert the part. If the Launch
move dialog option in the Insert
Part PropertyManager is enabled, the Locate
Part PropertyManager opens with the automatic mate constraint already
added.
You can also apply mates:
While inserting a body into a part, by selecting
Launch Move Dialog in the Insert
Part PropertyManager.
After the body is already in the part, using
Move/Copy
Bodies 
(Features toolbar).
Additional capabilities:
Apply multiple sets of mates to the same body.
Mates specified within different sets can conflict with each other. For
example, you can apply a perpendicular mate between two faces in one set,
and in a different set, apply a parallel mate between the same two faces.
Select several bodies at once to be positioned
by mates. The selected bodies move as a single entity. The bodies that
are not selected are treated as fixed