While slowly treadling, push the belt shifter lever and immediately stop treadling. The belt will be thrown off to the right side of the great wheel. The reason for stopping the treadle is that the belt will be put right back onto the great wheel if the shifter lever is released and the great wheel is still turning. To rebelt the sm, just begin treadling, in the proper direction, of course. You may need to just wiggle the belt a little between the handwheel and sm bed. In most cases, the belt is grabbed and put right back upon the great wheel. One never needs to get on hands and knees to rebelt these machines.
Johnm