Fill Or Kill
The fill or kill tool acts on any bet you place in the market and removes it if it is not matched after a set length of time.
Open the fill or kill tool by clicking on the + sign next to it and tick the box on the right.
Set the number of seconds that you want the bet to remain in the market for. As long as the box next to the tool is ticked your bets will disappear after this length of time unless they have been matched.