The engineering repair of a detected component crack to extend its usable life. It is better that a fatigue crack initiation does not occur over a machine’s operating lifetime; however, sometimes fatigue crack initiation cannot be prevented. When a crack is detected in a machine, it should be repaired, or the equipment should be replaced. A simple method of stopping crack growth is by drilling a stop-hole at the crack tip. When a long crack is initiated in a big structure or a production facility, it is better to arrest crack growth by applying patches. Metal stitching or metal locking is a simple but effective method used to repair cracks in cast metals without the need of welding.