When mounting side guiding rails on {HEAD ~ vertical wall surfaces} of a building it is often problematic to correctly align and space the various mounting brackets used in the mounting of {TAIL ~ a single rail} 
When mounting side guiding rails on { HEAD ~ vertical wall surfaces } of a building it is often problematic to correctly align and space the various mounting brackets used in the mounting of { TAIL ~ a single rail }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL