The enclosed trailer will still be listed as a business asset, just not in the section for items under $2500. 

If you had other items that cost under $2500, go ahead and complete that section.  When you are finished with that section, the next questions will allow you to enter the details about any item(s) that cost more than $2500.  These will be entered for depreciation or as a section 179 expense. 

Your trailer should be categorized as “Tools, Machinery, Equipment, Furniture” and then “Trailers and Trailer Mounted Containers”.  Then, you will enter the details about your trailer such as the cost and date of purchase.  Finally, you will be given your options for deducting the cost of the trailer. 

For more information about depreciation, please take a look at the following TurboTax article Depreciation of Business Assets.