Click on the Occlude button to bring up a dialog box,
  allowing you to specify occlude options for the
  transaction.

  This temporarily overrides any default occlusion you may
  have set in the Options menu.  After the current
  transaction, CMS uses whatever defaults you have set in
  the Options menu.

1  –  O d

  CMS operates on your library search list by searching
  through the library (or libraries) in the list.  If you
  have more than one library in the search list, CMS
  searches the libraries one at a time, in the order in
  which they appear in the search list, until a specified
  object is found.  Once the object is found, CMS performs
  the specified operation on the object. CMS will not
  continue to search for the object in any of the remaining
  libraries.

  When an object with the same name exists in more than one
  library in the library search list, CMS processes only
  the first occurrence of the specified object and ignores
  any later instances of that object in subsequent
  libraries.  Thus, the first instance of the object
  occludes any subsequent instances of that object.

  You can direct CMS to search for all occurrences of an
  object by deactivating occlusion for the object.

2  –  Occ etb

  The Elements button controls occlusion of elements. When
  this button is activated, CMS searches for and acts upon
  the first occurrence of an element found in a library
  (the first library that contains the element) in the
  library search list.

  If this button is off, CMS acts upon each occurrence of
  the element or elements found in the library search list.

3  –  Oc gtb

  The Groups button controls occlusion of groups. When this
  button is activated, CMS searches for and acts upon the
  first occurrence of a group found in a library (the first
  library that contains the group) in the library search
  list.

  If this button is off, CMS acts upon each occurrence of
  the group or groups found in the library search list.

4  –  Oc ctb

  The Classes button controls occlusion of classes. When
  this button is activated, CMS searches for and acts upon
  the first occurrence of a class found in a library (the
  first library that contains the class) in the library
  search list.

  If this button is off, CMS acts upon each occurrence of
  the class or classes found in the library search list.

5  –  Oc otb

  The Others button controls occlusion of other objects,
  including the element list, the group list, the class
  list, library attributes, history, and commands.

  When this button is activated, CMS searches for and acts
  upon the first occurrence of the object (or objects) in
  the library search list.

  If this button is off, CMS acts upon each occurrence of
  the object or objects found in the library search list.