Another question - how does 4x differ from the 3x in the wheel building thread? 
You pass your trailing spokes over 4 leading spokes as opposed to 3 till it goes in the desired hole 
Don't you mean 'under' dubber

4 cross ........ under 3 over 1
3 cross ....... under 2 over 1
first set of spokes are inserted the same for both 3 and 4 cross
