What weapon does Clyde use to kill his cell mate?

Clyde Shelton bargains with Nick Rice to give the location of Bill Reynolds, (Darby's attorney) in return for a 20 ounce Porterhouse steak (medium rare with all the trimmings) from Del Frisco's to be delivered at precisely 1 p.m., along with his iPod. Warden Inger demands multiple delays, resulting in the food arriving at Shelton's cell eight minutes late. Rice and Detective Dunnigan find Reynolds buried alive and only minutes dead, with Inger's delay causing him to suffocate, his oxygen tank having been set to shut down at 1:15. Dunnigan explains that because Shelton received his lunch at 1:08, they were 7 minutes late instead of getting to Reynolds in time to save him.

Meanwhile Shelton shares the steak dinner with his cellmate. Shelton palms the steak's T-bone and while distracting his cellmate with the iPod, murders him by using the T-bone as a push-knife. It gets messy and the Duxiana bed gets wrecked.

Edit to add information: The 'T-bone', including 'Porterhouse', is cut from the Short loin (top of the back). To cut a T-bone from butchered cattle, a lumbar vertebra is sawn in half through the vertebral column. The downward prong of the 'T' is a transverse process of the vertebra, and the flesh surrounding it is the spinal muscles. The small semicircle at the top of the 'T' is half of the vertebral foramen. This is a very strong bone and would make a very effective push-knife.