Cut each length of 1 meter band and not bringing it down into the underground subway, using special equipment to work in narrow and connect them to length.
Cut each loop length of one meter, then press down into the ground and then underground using special equipment working in cramped. And connected to each other until the desired length.
Cut each section, the length of the 1 meters underground and underground press using special equipment to work on ่แคบ. Connected until the desired length.