If you look closely at the components that make up your system, you will notice a series of pulleys and cables. The doors could not be opened mechanically without those pieces. Although the cables appear strong, they can break. More commonly, they slip off the pulleys due to tension, twisting, or other problems stemming from improper installation. Whether they break or slip, both situations will result in an inert door. If a cable has slipped from its pulley, you might be tempted to reposition it yourself. It is a simple operation. The problem is, it is also dangerous. You would be better-served by calling a technician with experience in automatic garage door repair.
