Assuming that have the same title in two departments /collections in your institutional repository
One appears under the Sub community [ Architecture and Planning] and collection [Journal Publication]
The other appears in the Sub Community [Biotechnology] and collection [ Journal Publications}
In my case the duplicates appears in Communities (1) [ Architecture and Planning and (2) Biotechnology.
Therefore I navigate to Research Publication (community) Architecture and Planning (sub-community) and Journals Publication (collection) homepage.
i.e. Research Publication/Architecture and Planning/Journals Publication
On the right side we see Item Mapper. Click on the item mapper which will take you to a new page.
After you have clicked on Item Mapper it will give you this page.
Now type the title in the space and search for the item. It will give you a new page.
Click on Add
Click on continue
Since we have mapped the item we will see two titles with the same name.
If we check both the titles, each of them will be giving different output. This item has not been mapped as it has a single collection with sub-community and it be deleted.
This item has been mapped as we can we two collections of different sub-communities
After having done this if we browse the title again we can see only one title in the list.