The Transfer gate is a symbol used to link logic in separate areas of a fault tree. There are two primary uses of Transfer gates. First, an entire fault tree may not fit on a single sheet of paper. (Or, to better view and organise them, the preference is to keep the individual trees small.) Second, the same fault tree logic may be used in different places in a fault tree. Through the use of Transfer gates, this logic can be defined once and then used in several places. To use a Transfer gate, a Transfer In gate is inserted in a fault tree and then linked to a Transfer Out gate, which represents the top gate of another fault tree.