anchor.diff:    do i=1,iu
       ix=ic(i)-nblo
       if( ix.gt.0 ) then
  -      write(lout,"(a,i8,1x,a,1x,f15.6,1x,i8)") "APER> ",i,bez(ix),dcum(i),kape(ix)
  +      write(lout,"(a,2(i8,1x),a,1x,f15.6,1x,i8)") "APER> ",i,ix,bez(ix),dcum(i),kape(ix)
       else
  -      write(lout,"(a,i8,1x,a,1x,f15.6)") "APER> ",i,bezb(ic(i)),dcum(i)
  +      write(lout,"(a,2(i8,1x),a,1x,f15.6)") "APER> ",i,ic(i),bezb(ic(i)),dcum(i)
       end if
     end do
     write(lout,"(a)") "APER> dumpMe -----------------------------------------------------------------------------"
  
positive.code:       write(lout,"(a)")    "APER> ...no need to insert an upstream marker - no shift of downstream entries required."
      end if
    end if
  
  ! downstream marker
    iuold=iu
    call contour_aperture_marker( iElDw, .false. )
  ! the addition of the downstream aperture marker may have shifted by one the downstream entries
    if( iu-iuold.ne.0 ) then
  ! NB: if lAccrossLatticeExtremes, the downstream marker is almost at the beginngin of
  !     the lattice structure! Hence, if a new entry has been inserted,
  !     the upstream marker (towards the end of the lattice structure) is
  !     shifted by 1
  
negative.code:   iElDw=itElDw
  ! markers accross extremes of lattice structure?
    lAccrossLatticeExtremes=iElUp.gt.iElDw
  #ifdef DEBUG
    write(lout,*) "check 00: il, iu, iuold, iElUp, iElDw, ic(iElUp)-nblo, ic(iElDw)-nblo", & 
         il, iu, iuold, iElUp, iElDw, ic(iElUp)-nblo, ic(iElDw)-nblo
    call dumpMe
  #endif
  
  ! upstream marker
    iuold=iu
  