All products, men and supplies, as well as recoverable ore, travels up and down the shaft in a cage. When the hemp rope or chains broke, the cage would plummet uncontrolled to the bottom of the shaft, killing its occupants or destroying its load. Cages were open to the front and rear, with I-beams on both sides to support the floor. The outside of the I-beams slid through wooden guides up and down the shaft, top to bottom. Spring loaded cages were designed with two swivel rods at the top of the cage, one each attached to the I-beams through bolts and lifted in the center. The outside of the rods were designed to be wider than the cage with a bulbous, round head at the end, notched with teeth molded into the rods. The weight of the cage being lifted, lifted the rods, released the teeth and tightened the spring, allowing the cage to move freely. If the chain or cable broke, the springs would force the rods down and the teeth would dig into the wood, stopping the cage.