Drop
When a portion of mould falls from an over-hanging surface, it is spoken of as a "drop."
Drop-gates are gates which connect with the casting from the runner basin vertically. They may be so placed for mere convenience, or with the view of obtaining a clean casting by constructing a basin above that may be instantly filled with metal, and thus allow the casting to fill from the bottom, with no possibility of dirt entering the mould. See GATES; VENTING.