knob on mast?

[Hugh Brodie]

I know it's probably a stupid question. There's a big knob thing on the port side of the mast about the size of a large plum. Some mysterious sheet or halliard must get turned around this but I can't quite see what. (probably a spinnaker line)
Please put me out of my misery!

Thanks,
Hugh Brodie
Cunning Plan
s/v CDTy #794



h.b@aarpc.com