Some valves have a hole from the outside of the ball through to the bore. This allows pressure equalization between the body cavity and the bore. When in the open position, if you open a bleed port, you get full line pressure coming out. Some people don't like that.
If you would speak in complete thoughts you might get meaningful answers. Was that statemenat made by the Roadrunner upon looking at an Acme valve? Was it in a maintenance manual? Was it in a sales brochure? Did it come to you in a drug dream?
If a valve ball (or gate, plug, etc.) is provided with an equalizing hole, it allows a pressure balance across the valve seats while in the open position, and effectively lowers the valve torque when stroking to the closed position. This is why many valve manufacturers will include it as a standard feature.
By being present however it prevents the valve cavity from being blown down while in service. Many operators want to blow down the body cavity with the valve in the open position as a means of verifying the integrity of the valve seats.
