The injection under pressure of a variety of materials into a BOP to seal off upward flow such as in the case of the BP oil spill in the Gulf of Mexico. At first BP injected mud alone into the well, but then started adding rubber golf balls and scraps to the mud to help block leaks in the well. Some of the junk-shot pieces are fibrous and small, and others are larger rubber balls. The goal of the junk shot is to force-feed the preventer, the device that failed when the disaster unfolded on April 20, 2010 until it becomes so plugged that the oil stops flowing or slows to a relative trickle. That would be followed by a “top kill,” the pumping of heavy mud into the well to overcome the pressure of the rising oil, followed in turn by cement that would permanently seal it.