There are two types of fillet welding gauge Metric &Inch , one end is metric , the other end is inch Inch. Both end are inch China manufacturer Part No:WG-211 Manufacturer: Rok International Industry Co., Limited How to use the gauge: Welding is a very interesting line of work and take actually training to understand everything involved. You can easily learn how you would use a weld fillet gauge by attending classes. However, if a weld is convex, you only need to use the end of the gage,An inside corner weld between two perpendicular pieces of metal is called a fillet (fill-it) weld. The fillet weld needs to be at least the thickness of the thinnest material being joined by the weld. For example, if you are welding a 1/4-inch metal plate to a 3/16th-inch metal plate, the fillet weld will need to be 3/16ths of on inch across and have a 3/16th-inch throat depth. A fillet gauge measures the size of the fillet weld to ensure its structural integrity A Read the weld specification sheet to see if there are any specifications for the fillet weld size. Unless otherwise specified, assume that the fillet weld needs to be the same size as the thinnest piece of metal being welded.