The document SheetBridges.pdf has been placed on the website
It shows the assembly of sheet bridges and how they function in the
formation of the pleated sheet. The bridges, which connect the strands
of a pleated sheet, permit intervening strands to pass under or over.
A one strand bridge contains just four main chain units. Its span can
be extended to permit 6, 11, 16, ... sheet joined strands to pass
unimpeded. A sheet consisting of four pairs of parallel strands
arranged so that adjacent pairs are anti-parallel is shown. The bridge
arrangement for this eight strand sheet is depicted schematically.