Re the blocks on the rotation spanner;
a line ties off on a pad eye on starboard side of the beam, go through the block on the port side of the spanner and back to a cleat on the starboard side of the beam via the cheek block next to the pad eye. Mirror this for the other side of the boat.
this is so that you can pull a line from the tramp and the mast will rotate to 90 degrees [along the beam] when sailing down wind. REMEMBER to release each time you gybe!

These can also be used to over-rotate a bit upwind in light airs. Remember to let them off each time you tack!