The shaving pony holds your rim in place while you scarf the ends with a draw knife. The lever on the left lifts up to allow the reed to enter under the wheel, then pushes down with the help of the rubber bands to hold it tight.  The guide slides back and forth to help hold the reed in place but doesn't hold it tight.  You can then use a drawknife to scarf your rim.  The circle of hardwood on the right is a place to secure the shave pony to the table with a "C" clamp.  Your rim is held at the perfect angle for a beautiful even trim.