A welding symbol connects the joint on a drawing to the weld instructions. The reference line carries information, the arrow points to the joint, and the location of the weld symbol communicates which side is intended under the drawing convention. This text-only guide describes selected AWS-style elements using a manufacturer’s reading guide. It does not reproduce symbol artwork or replace the standard identified on a drawing.

Basic Welding Symbols Reference

Read the reference line and arrow together

The horizontal reference line is the anchor for the welding symbol. The arrow connects that line to the joint being specified. First identify the exact joint member the arrow touches; that physical side is the arrow side. Read the weld instruction relative to the reference line only after confirming the drawing’s governing symbol system.

In the AWS convention described by MillerWelds, a weld symbol below the reference line refers to the arrow side, while one above refers to the other side. The rule is independent of whether the arrow slopes up or down. This placement is easy to misread when a drawing is rotated, scanned poorly or assembled from files produced under different standards.

Use the tail for supplementary information

The tail is at the end of the reference line opposite the arrow. It can contain a process designation, electrode information, a procedure reference or another note. A drawing may omit the tail when no note is needed. When it is present, follow the referenced specification or welding procedure rather than interpreting a short note in isolation.

The symbol alone does not provide every fabrication instruction. Joint preparation, backing, sequence, preheat, interpass temperature, filler metal, shielding gas and inspection may be defined elsewhere in the drawing set or welding procedure specification. Check referenced documents before releasing work.

Recognize supplementary marks

Miller explains that a flag at the junction of the arrow and reference line marks a field weld, made at the site during erection. An open circle at that junction indicates that the weld continues all around the joint. These marks add information but do not specify weld size, process qualification or acceptance criteria.

Some older drawings may use another mark for field welding. A project legend or design standard should resolve the intended meaning. AWS A2.4 specifies welding-symbol conventions, and the applicable edition should be named by the contract or drawing. Do not transfer a familiar interpretation to an unfamiliar international system without checking it.

Do not confuse a weld symbol with a complete procedure

A basic weld symbol identifies type and location of weld information; dimensions and supplementary details may be added according to the selected standard. The symbol does not certify that a joint meets a code, nor does it define how to qualify a procedure or welder. Those requirements come from the applicable fabrication code, procedure specification, contract and inspection plan.

A fillet symbol and size can indicate nominal weld geometry, but a drawing may also need length, pitch, contour, finish, process and inspection information. A groove symbol may need dimensions and preparation details. If a value or note is missing, ask the responsible engineer or welding coordinator instead of filling the gap from a generic chart.

Check the drawing standard

AWS-style placement uses the above/below relationship to the reference line. ISO systems can add a dashed identification line and interpret placement differently. Imported drawings may use local standards or company conventions. Look for a title-block note, drawing legend or specification reference; if none is present, confirm the governing system before fabrication.

The table focuses on basic elements described by Miller. It leaves out detailed symbol glyph charts, dimensions, joint designs and process abbreviations. The AWS preview identifies the standard scope, while the full controlled publication and project documents govern complete interpretation.

Source and scope

Element placement and supplementary-mark descriptions were checked against MillerWelds’ guide. The standard reference is AWS A2.4:2020; its preview is not the full standard. The text table is an original summary of selected meanings and includes no copied standard drawings.