Initialised by the routine at 35090, checked by the routines at 36307 and 36796, and checked and updated by the routines at 36564 and 37310. Possible values are:

Value	Meaning
0	Willy is not on the rope
3-32	Willy is on the rope, with the centre of his sprite anchored at this segment
240-255	Willy has just jumped or fallen off the rope