The rigging of a sailing ship is operated with blocks and tackles. For a three-master around 1,000 blocks were required, of which the largest (the Voyol blocks) was up to 5 feet long in a three decker, and the smallest (the signal halliard block) only 3ins.
        A block consists of a shell -this could be made in one piece or assembled from several components -which was always made of wo until the middle of the 19th century. After this time the shell was occasionally made of metal. The shell contained a pulley, or sheave, over which the rope ran, and which rotated on a pin. The manufactur of blocks with rotating pulleys is hardly to be recommended -except for very large-scale models -and is technically well-nigh impossible
in any case.
         The drawing on the right illustrates how model blocks are made: they are first cut from a strip of very hard, dense wood (box, walnut, perhaps pear or olive) to the width and thickness of the blocks. Using a circular saw (indispensable for making blocks) cut crosswise grooves spaced out along the length of the strip (do not cut right through). The grooves for the swallows and for the strops are cut next, again using the circular saw, and the holes for the ropes drilled. The edges are rounded off with glasspaper, and the cross-cuts between the blocks widened with a triangular file. The individual blocks can now be separated from the strip, and sanded to a more rounded shape.Until 1815 blocks were generally rounded in shape; on merchant ships they remained so until later , while warships after 1815 preferred a more angular shape of block. There were also a whole series of special block shapes:
         Ramshead blocks (see HALYARDS), lift blocks (see LIFTS), shoe blocks, sheet and                shoulder blocks (see SHEETS), clew-line blocks (see CLEW LINES) and snatch blocks             (see BOWLINES).
Sheet blocks and lift blocks were only used on the Continent, British practice was to use individual blocks stropped together instead (see RUNNING RIGGING).
    Block sizes
Sizes of blocks are given in mm.
The information given here is an approximate guide as variations temporal and national have not been included. There was also a certain tendency to make blocks for rope thicknesses of 6 to 13mm rather larger, and from 38 to 76mm rather smaller, than stated.