The feet themselves are a grommet I found at the hardware store. The stem is a screw. The cross piece has a "T" nut in it that the screw goes into and sets the height. The nut on top acts like a lock nut. The motor assembly has 4 small rubber feet, non-adjustable, so the 3 feet on the turntable body have to adjust to get the belt to ride the platter correctly.
There certainly isn't any magical design to it. If I had some better feet, I might use them, but in the mean time, this works even tho its not really "pretty" looking.
'ner