Just a quick couple questions about these types of orders... If i enter a buy on open order before the market opens will i get filled the shares i input 100% of the time? Or is there a chance that i will not get filled because there is not enough shares to fill me. Also Can you go short on the open by entering a sell at open order? Finally... As per question 1, are the orders filled on a first come first serve basis... ie inputing orders at 8am will have a better chance of being filled than orders at 9:25? Thanks alot.