The predominant method of longwall mining in Australia is longwall retreat system. In retreat longwall mining, two sets of entries are driven between 100 to 250m apart. When the entries have been driven a predetermined length, say two kilometres, they are connected and a rectangular longwall block is outlined. The longwall face is then installed and as mining continues into the panel, back to the original development, the entries are allowed to collapse behind the face line to form part of the goaf. The gate entries are known as main gate and tail gate. Generally the main gate contains the belt conveyor and the pantechnicon for facilitating power and logistics to the longwall face. A typical retreat panel layout can be seen opposite and the details of longwall equipment and installation are explained in the key references.