Matrices released from the magazine, and spacebands released from the spaceband box, drop down into the assembler. This is a rail that holds the matrices and spacebands, with a jaw on the left end set to the desired line width. When the operator judges that the line is close enough to full, he raises the casting lever on the bottom of the keyboard to "send" the line to the casting section of the linotype machine. The remaining processing for that line is automatic; as soon as the finished line has been transferred to the casting section, the operator can begin composing the next line of text.