Checking fillet weld leg length and fillet weld throat dimension. G.A.L. Gage 8 Piece Fillet Weld Sets These gauges come in a variety of sets with sizes ranging from 1/8 of an inch to 3 inch in both inch and metric sizes. To use these gauges, verify the fillet weld leg length as noted in the specifications and use the fillet weld gauge of the same size. In this case, the specifications call for a 1/2 inch fillet weld. Using this end of the 1/2 inch fillet weld gauge, we can check the fillet weld