Welding Term Definitions and Glossary from PraxairDirect Welding Terms Glossary. Hot Crack – A crack formed at temperatures near the completion of weld solidification. Hot Pass – In pipe welding, the second pass which goes over the root pass. Inclined Position – In pipe welding, the pipe axis angles 45 degrees to Basic Welding Terms - keenovens Basic Welding Terms. Face - On plate or pipe welding there is a ROOT PASS, HOT PASS, FILLER PASS, and CAP. The root penetrates through the back of the plate, the cap is on the surface which you are welding, which is the face. Fan: Welding machines have a fan to cool the machine down and keep it from overheating.