Reference line and arrow

How to read it

On a drawing, a welding symbol is built on a reference line, with an arrow connecting the line to the joint to be welded. The reference line carries the weld symbols, dimensions and other data. The direction of the arrow has no bearing on what the reference line means, and the information along the line is read from left to right.

A weld symbol below the line, on the side toward the reader, is on the arrow side: the weld goes on the side of the joint the arrow touches. A weld symbol above the line is on the other side of the joint. Symbols on both sides of the line mean welds on both sides of the joint.

Also searched as: arrow side, other side, welding symbol parts.

Weld symbol and welding symbol

The two terms mean different things. The weld symbol is the small ideograph for one type of weld, such as a fillet. The welding symbol is the whole assembly, which can include the reference line, the arrow, weld symbols, dimensions, supplementary symbols, finish symbols, a tail and a specification or process.

Differences by country or standard

These pages follow the American Welding Society's system, used across the United States. Drawings made to the international standard, ISO 2553, use a dual reference line instead: a continuous line with a dashed line beside it, and the dashed line can be drawn above or below the continuous one. A symbol on the continuous line means a weld on the arrow side of the joint, and a symbol on the dashed line means a weld on the other side. India's IS 813:1986, which draws on ISO 2553, sets out the same rule.