To use the gauge, you would place the "Hi" notch over the weld bead and check to see if the bead fits snugly inside the notch. If the bead is too large for the "Hi" notch, you would then try the "Lo" notch to see if the bead fits inside that one. If the bead fits the "Lo" notch, but not the "Hi" notch, then the weld bead is within the acceptable range for the welding procedure. Hi-Lo welding gauges are commonly used in the welding industry and are an essential tool for ensuring that welds are of the proper size and quality. They come in various shapes and sizes, and some gauges may have additional features such as measuring fillet weld throat size or measuring undercut depth. Kristeel brand Hi-Lo welding gauges is one of the premium products avaialable in the market offered by Apex Commercial Corporation.