A prime rib roast (whole standing rib roast) features from between 6 to 12 ribs. Since the ribs get bigger as they get closer to the shoulder area, the small end is often called the loin end or a first cut. Most of the time the butcher will cut off the chine bones located on the bottom of the roast for the buyer, since they have heavy machinery that makes the job much easier. Any person can do this with the help of the right knife and the needed knowledge.
Things You'll Need
Lift the roast to an upright position and trace the rib bones with the electric knife starting at the bottom and moving towards the base. This will make the ribs stick out a bit more from the meat and make it easier to cut them off from the chine.
Cut through the chine where it meets the ribs and do your best to remove the cartilage as well. It might be easier to first hack through the larger bones of the chine and then remove the smaller parts.
Use the electric knife to remove the chine as it will now be accessible to grab by hand and starting to pull away from the ribs. Cut in an upward motion using the weight of the roast to your advantage.