"The basic idea of long wall coal mining was developed in England in the 17th century. The coal would be undercut along the length of coal face then removed as it broke away and timber props inserted to control the fall of the roof behind the face. This low tech method remained basically unchanged until 1900 when machinery was introduced to this form of coal mining and a rubber conveyor belt ran parallel to the face. Other innovations were the introduction of the electric coal cutter to undercut the face and electric drills to drill holes for blasting to drop the coal. Manual labour i.e coal fillers was used to shovel the downed coal onto the conveyor belt and place wooden props to control the fall of the roof. This method of winning coal became obsolete in the early 70s when it was overtaken by new coal cutting methods. Fillers worked in pairs and were allocated their own stretch of face to work. There could be 20 fillers to a 200 yard face giving each 10 yards of coal to shovel onto the conveyor belt. Fillers were mostly on piece work and paid according to their output."