MFI goodbye !

I'm not a holder of MFI, but I see it as a high risk entity. If I were a company and interested in buying Howdens, I'd wait for the group to collapse and I'd be valuing Howdens at considerably less than I've seen it valued earlier on this threrad - my reasoning being that if 40% of its' sales are to an ailing (or collapsed) business, Howdens ongoing sales and profit must surely be sustantially lower than historically. Given the above, I'm interested in "betting" that MFI SP will fall. My only investing historically has been buying shares that I think will rise (some of which I've got right and others I put down to experience!). Can someone explain how I make a downward bet (a short?) and what would happen if the shares were suspended (most likey due to Administration) before I crystalised my position?