Sitecore includes support for copying presentation details from one item to another, but what about copying an item's Shared Layout to its Final Layout? Whether you're looking to copy Shared Layout details to the same or a different item's Final Layout, this trick will work for you.
Since both the Shared Layout and Final Layout details are stored in XML fields on the item, you are able to view, copy and edit the raw XML by viewing the "Raw Values" for the item. The Shared Layout details field is named "Renderings", whereas the Final Layout details field is named "Final Layout".
All you need to do is copy the raw value of the "Renderings" field over to the "Final Layout" field and you will have effectively copied the Shared Presentation Details to the Final Presentation Details.