An employee was emptying trash from a small collection unit (hopper) into a much larger collection unit (roll-off dumpster). This required the employee to stage the hopper up and over the roll-off dumpster with a forklift and then dismount the forklift to manually pull a mechanical lever that releases the hopper vault and dumps the hopper contents into the roll-off. The employee grabbed the releasing handle with his right hand and placed his left-hand fingers on the bottom cross-section of the hopper between the bottom of the forklift fork and the hopper frame. When he released the hopper vault, the hopper frame sprang suddenly and violently upwards until it stopped by the bottom of the fork and created a pinch point. The employee's left-hand ring, middle, and index fingertips were caught and amputated in the pinch point.