"Threading Pulleys" is good enough I suppose....personally I'd prefer the term "reeving of blocks", but not to worry.
As the previous poster said, the blocks (for a 3 sheave set-up) are right angles to each other, however, stopping chafing is not the prime reason for this. It is so the blocks can be reeved so the hauling part can exit out of the top centre sheave. This keeps the blocks upright when the weight come off and so prevents "toppling".