Iron ore price, page-43334

You need to fullfill the short based on a time period not on its price like a put or a call option.
e.g FMG is $22.58 and I pay you $100 to borrow your FMG shares for 6 months, I sell the shares but because I am borrowing the shares in 6 months I will need to buy them on-market to give them back to you. If FMG is over $22.58 I lose because I have to spend more then $22.58 to give you the shares back but if I can talk the price down and its below $22.58 I can give you your shares back and make a proift. As a long-term holder you don't really care (ignoring Div in my example).

Why anyone would short FMG is beyond me, FMG themselves have no idea how SP will go because they don't control the IO price. However with companies that are overhyped shorting makes more sense e.g. Afterpay, Zip, Kogan