How to: Overlap graphic drawing objects in a worksheet.
Solution:
Select an object, then select 'Placement' from the 'Format' menu. Select either 'Bring to Front' or 'Send to Back'.
1) Select (click on) one of the objects, and move it to where it overlaps with the other object(s).
2) Select the 'Format' menu and select 'Placement'. (This displays the Placement submenu.)
3) Select 'Bring to Front' or 'Send to Back'.