Attachment Of Drawings in BOMs

How to attach a document to a BOM ?
Now one can attach a document to a BOM in one of the following three ways…
1) Attach document as an item in the item overview,
2) Attach document to an item and 
3) Attach document to the header material.
1) Attaching document as an item in the item overview:
…go to the `General Item Overview' screen
…select the tab page `Document'
…enter item category `D'
…dropdown and select the document you want to attach 
…the system automatically selects the respective document type, document part, document version and document description
…the system also enters component quantity `1' and component unit of measure as `PC' by default.
2) Attaching document to an item:
…go to the `General Item Overview' screen
…select the particular item by F2 
…the item all data screen appears 
…go to tab page `document assignment'
…dropdown and select the `document type' you want to attach …dropdown and select the document you want to attach 
…the system automatically selects the respective document part, document version and document description
3) Attach document to the header material:
…go to header overview screen 
…go to tab page `document assignment'
…dropdown and select the `document type' you want to attach 
…the system automatically selects the respective, document part, document version and document description
Pre-requisites…
…create document by transaction CV01N  
…Customizing settings…in document management customizing determines which objects can be assigned to documents per object type.
…go to IMG -> cross-application components -> document management -> control data -> define documents type
…select the document type for example `DRW'
…select the sub dialog `define object links'
…select new entries and enter following objects…
…'STPO_DOC' and screen `257'(linking document to BOM header) …'STKO_DOC' and screen `258'(linking document to BOM item) …now documents can be linked to BOM header as well as BOM item.