Reading Weld Symbols
Weld symbols are the universal language of fabrication drawings. Every weld symbol is built on a reference line — a horizontal line with an arrow pointing to the joint location. The arrow side of the reference line indicates the weld is applied on the side of the joint where the arrow points; the other side (tail end, above the line) means the opposite side. The weld symbol itself sits either below (arrow side) or above (other side) the reference line. Common weld symbols include the fillet weld (triangle), groove welds (V-groove shown as two angled lines), plug or slot weld (circle), and backing bar (rectangle). Dimensions appear to the left of the symbol: size (leg for fillet welds, depth for groove welds). The length of the weld appears to the right, and if intermittent, both weld length and pitch (center-to-center spacing) are shown as "weld length – pitch". A circle at the junction of the arrow and reference line means the weld is all-around the joint. A flag at the tail means field weld. A tail fork carries supplementary information such as the welding process (SMAW, GMAW) or the WPS number. Practicing symbol reading with actual shop drawings is the fastest path to fluency.