Time-of-Flight Diffraction (TOFD) is a non-destructive testing method used to detect and quantify defects in welds and other metallic components. It uses a pair of ultrasonic transducers to send short pulses of sound into a material and measure the time it takes for the sound to travel through the material and reflect back. By measuring the time it takes for the soundwave to travel to the defect and back, the size, shape, and location of any defects can be determined. TOFD is an effective method for detecting cracks, porosity, and other discontinuities in welds, making it a valuable tool in quality assurance and quality control.