Fig. 118 shows a typical small green sand mould in a two-part flask. This is a mould of the pattern shown in Fig. 108. The upper half of the mould is the cope and the lower half is the drag or nowell. The two parts of the mould are separated at the parting. The casting is made hollow by the core, resting in its bearings. A number of vents are punched by a small steel wire before the pattern is removed. The vents conduct away gas and steam generated in the sand by hot metal, and prevent the escape of these into the mould. Before pouring, the mould is weighted down to keep the cope from floating. Metal is poured from a ladle into the basin, entering the mould through the runner and gate. Many moulders designate the runner as the sprue. As pouring continues, metal gradually fills the mould and rises to the top of the riser. Vent gases escape at the top, around the parting and along the bottom board. Air escapes from the mould cavity through the riser as metal is poured in: A small vent channel runs through the core, conducting gases to the parting. A single flask often contains several moulds of small castings, all run from the same sprue.