While the hub is locked down in the press, Sandwich tries to move the upright up and down to make sure there is NO play in the upright. At the same time, he is making sure there is about 25 inch pounds of drag on the preload of the bearings by rotating the upright side to side. Finally, he gives the assembly a 360 degree turn to make sure nothing is caught or binding up all the way around. It is all quite a delicate dance, but with experience it is definitely easier to do.
