Guided Wave Testing Guided Wave testing (GWT) is one of latest methods in the field of non-destructive evaluation. The method employs mechanical stress waves that propagate along an elongated structure while guided by its boundaries. This allows the waves to travel a long distance with little loss in energy. Nowadays, GWT is widely used to inspect and screen many engineering structures, particularly for the inspection of metallic pipelines around the world. In some cases, hundreds of meters can be inspected from a single location. There are also some applications for inspecting rail tracks, rods and metal plate structures. Although Guided wave testing is also commonly known as Guided Wave Ultrasonic Testing (GWUT) or Long Range Ultrasonic Testing (LRUT), it is fundamentally very different from conventional ultrasonic testing. Guided wave testing uses very low ultrasonic frequencies compared to those used in conventional UT, typically between 10-100 kHz.