A fillet weld is a type of weld used to join two pieces of metal at a right angle. It is typically triangular in cross-section and is applied along the joint where the two pieces meet. Fillet welds are commonly used in structural applications, such as in the construction of buildings and bridges, due to their strength and versatility. These welds can be made using various welding processes, including MIG welding, TIG welding, and stick welding. The size and shape of a fillet weld can be adjusted based on the requirements of the project, making it a popular choice for fabricators and welders in many industries.