The dressing of the sarsens seems to have been carried out in several stages of increasing delicacy.
Initially, the rough and irregular surface appears to have been reduced by working parallel grooves about 9 ins. wide and 2 to 3 inches deep, generally running longitudinally, using the larger mauls of 20 to 30 Ibs. in weight.
Examples of tooling left in this state can be seen on the upper (outer) face of stone 59 as shown above and on the lower part of the outer face of stone 54
Image credit: Chance – March 2008
Even more so than in this picture of stone 59, stone 54 shows what appears to me to be clear signs of cleaving, rather than working grooves with mauls. The planes of cleavage appear on the south and west faces of 54, possibly creating the "face" that appears halfway up the west side. Working massive stones (that in all likelihood had huge volumes of superfluous rock beyond the desired shape) with mauls always appeared to me to be very unlikely. Surely the basic shaping would have been done by cleaving the rock using wedges or local heating/cooling? These were a people who were supremely skilled at working with stone, and would surely have worked out better methods for shaping a huge boulder than the body-breaking labour of mauls. Obviously mauls would be used to finish the work ... but for the whole job? I think it's very unlikely.
I think that what we see on stone 59 are the remnants of the original cleavage planes that have been smoothed into the surface we see now.