The Blade support device is used to get the hollowness on your skate centered by controlling the vertical position of the skate holder. When sharpening a skate hollow, put the skate blade on top of the roller.
SRK PRO has an exact scale wheel that ranges from 2.5 to 4.2 mm. Turn it to the skate blade thickness to get hollowness exactly centered.
By using a guide arm holding the skate blade, and a blade support roller just in front of the grinding wheel, the SSM-2 models will position a hollow very precisely using only one height adjustment point. This is so even if the blade is not completely straight (which it almost never is). No other design can match this. Furthermore there is no possibility that the hollow will be formed diagonally along the blade.