1 - Pick up the Arrow tool and select the half of the object you
separated in the previous tutorial (A).
Step 2 - Choose
Modify>Group (from modify on the menu bar) When
you do this a blue rectangle appears around the object indicating
that this is a grouped object (B).
Step 3 - Drag
the grouped object over another object (C).
Step 4 - Deselect
it by clicking on a blank section of the stage.
Step 5 - Click
and drag the first object off the second one (D).
Step 6 - With
the first object still selected choose Modify>Ungroup
Now drag the first object back on top of the second one. Click to
Step 7 - Select
it again, and now drag it back off... notice how you're now missing
part of the second object? (F).