The 05-Design folder is used to store design drawings. 

Plan and detail drawings are stored in the A-XREFs sub-folder while sheet set (title block) drawings are stored in the B-Sheets sub-folder.

Plant 3D and Revit models are stored in the C-Models sub-folder.

Documents and important emails are saved in the E-Correspondence sub-folder.

Working drawings and files are saved in the D-WIP (work in progress) sub-folder.