Can anyone help ? I am about to begin lining and insulating a brick built shed to use as a workshop. I am OK with moisture barrier, batten, insulation and boarding but I have been told I should 'blackjack' the end of the shed where there is previous evidence of moisture . This end is open to the prevailing wind and so the rain drives at it (I live on the top of a hill). I understand that this should be done inside and out to help but the question is, what is 'blackjack'? Is there a manufacturer name, and where should I look ? Cant see it in the sheds (b&q, wickes etc). I want to be able to ask for the correct thing !