chain eye 129 and the first end of fourth chain 127 is secured within fourth frame end chain eye 131 the second end of first chain 124 is attached to trench box first attachment point 132 the second end of second chain 125 is attachable to trench box second attachment point 133 similarly the second end of third chain 126 is attachable to trench box third attachment point 134 and the second end of fourth chain 127 is attachable to trench box fourth attachment point 135 at this point h clips 157 and 158 are removed and first trench box 11 raised by operation of first hydraulic arm 110 to split the boxes as shown in fig5 as trench shoring transport device 10 advances pipeline p will abut first chain 124 and third chain 126 at this point h clip 159 and h clip 160 shown in fig4 are disconnected and upper trench box 11 and lower trench box 150 are supported entirely by first chain 124 second chain 125 third chain 126 and fourth chain 127 first trench box 11 may be raised or lowered as required by operation of first hydraulic arm 110 so that h clip 157 and h clip 158 shown in fig4 may be reconnected at this point the second end of.