Shipped on board and clean on board bill of lading

I would like to explain the difference between shipped on board bill of lading and clean on board bill of lading on this page. 

The reason I would like to write about this topic is that some issuing banks demand "shipped on board" bills of lading, whereas others demand "clean on board" bills of lading under "letters of credit" payments.

Exporters are getting confused, when carriers issue a "shipped on board" bill of lading where the letter of credit requires a "clean on board" bill of lading or vice versa.