coupled between the frame and the planks this shield serves to excavate an open topped trench and behind the shield is a receptacle connected to move with the frame this receptacle is a substantially closed vessel resembling a bath tub in cross section with an open top permitting a pipe section to be lowered therein a rear end wall of this receptacle has an opening therein which enables the pipe section to be joined up to the end of another pipe section previously installed at the end of the pipe line application_number US 59445375 A description a composite pipe line for water mains sewerage or other purposes is composed of individual pipe sections or elements 10 arranged end to end and installed with the aid of the apparatus depicted in the drawings the individual pipe sections 10 which can be pre fabricated from concrete are laid in an open trench and are provided with location means such as the stepped tongue and groove connections on facing ends as shown in fig1 to locate each section 10 against the previously installed section 10 as the pipe line advances the installed and joined sections 10 are covered by soil or a similar filling denoted 11 in fig1 to reconstitute the ground surface so that the pipe sections 10 are buried beneath the ground surface this means that only a sufficient length of open.