Abstract: Method for joining sheets or panels of polyolefin is provided in which a layer of additional material is placed between heated polyolefin sheets or panels to be joined; the additional material being heated to a temperature sufficient to impart a sufficient level of heat to the surfaces of the polyolefin sheets to permit effective welding of the sheets to the additional material through the medium of a continuously operating pressure applying device.

Abstract: Method and apparatus for placing a horizontally elongated flexible material in vertical position in a trench are provided in which a portion of the trench is cut and the material placed therein. The open trench is then filled and the next section of the trench is cut and material placed therein. The process is separated until the desired length of the trench has been cut and the material has been placed therein. A cassette is provided which contains the material. The cassette has a slot to permit the material to pay-out as each section of trench is cut.