These can be made, and known, as either a Wire-Cut Brick or a Pressed-Brick. The Wire-Cut is produced by extruding the prepared clay, by means of a screw in the pug mill, through a die of brick dimensions. The extruded column of clay passes on a conveyor to a metal frame fitted with a number of parallel wires that cut the column into brick thickness; identified by wire marks on the brick bed and no frog. Pressed Bricks are made, with a semi plastic clay, by feeding clay into the tops of moulds in a press, which may be single or multiple, and compressing it vertically upwards with a ram which lifts it out of the mould. They may be formed with one, or two, frogs and are generally denser than a wire-cut.