Welding Symbols Introduction (Definition and Symbol Placement) 👨‍🏭 2022

Welding symbols are an important to quickly pass on information. 

Note: Welding symbology is based on the AWS A2.1 and AWS A2.4 standards.


Symbology can be defined as:

A set of lines, symbols and digits used in technical drawings to indicate some characteristics of welded joints.

But what is a symbol?

It is something that, by the principle of analogy, represents or replaces something else.

Welding symbols are drawings that represent guidelines for the welding process. 

They are used to save space and work in project drawings and, at the same time, symbols make drawing interpretation faster and easier. 

Symbols provide all necessary information for welding, such as: geometry and dimensions of the chamfer, weld length, whether the weld should be performed in the field, etc. 

Below is a basic structure for transmitting this information:

(1): Welding in the opposite side of the arrow.

(2): Welding in the same side of the arrow.

(3): Tail.

(4): Arrow.

Reference line

The reference line is a symbol and the base on which all other weld symbols (or instructions for performing a weld) are placed. 

Without it there is no welding symbol.

Symbols are used to indicate different actions, depending on its location.

Note: They may be placed above or below the reference line.

The reference line must be horizontal and the arrow line must have an angle as shown in the picture below:

Broken Arrow

A broken arrow is used when we have a specific member of the joint to be chamfered. And the arrow's job is to point to that member.

NOTE: ANSI/AWS A2.4 standard also states that arrows do not need to be broken in the following situations:

  • When the side to be beveled is obvious.
  • When there is an option to chamfer one or another of the members that make up the joint.

Multiple lines

Multiple reference lines are used to contain the information regarding successive welding operations.

The order in which these operations should be performed is determined by how close the line is to the arrow.

The first operation will be the one indicated by the nearest line and so on.


The arrow connects the weld symbol reference line with the joint to be welded.

In the first example given, the arrow points down and to the right, but many other combinations are allowed as long as the reference line remains horizontal (see examples below).


References such as specifications, welding processes, procedure number, directions and other data may be indicated on the tail of the symbol.

If such references are not used, the tail can be left without it.

It is common to use the tail to indicate the welding process or the consumable to be used.

Note: You can only insert information in the tail that does not have its own pre-defined place (Please look at the overview picture below).

Symbol placement

Weld symbols are positioned above or below the reference line depending on the location of the arrow in relation to the joint, namely:

  • Symbol below the reference line corresponds to a weld performed on the same side as the arrow points (2) or (6).
  • Symbol above the reference line corresponds to a weld performed on the opposite side to which the arrow points (1) or (7).

This is due to the fact that we often have welding on both sides. It would also be harder to use both symbols on the same side.

(6): Same side
(7): The other side


Welding involving features on both sides of the joint, have a symbol on both sides of the reference line.

Overview and Summary

In addition to the reference line, arrow, and tail, we have basic symbols, supplementary symbols, and dimensions or other weld data. These will be better explained in other articles.

The picture below shows a the standard locations for the various elements of a weld symbol.

Important Tips:

  • Any element of a weld symbol can be above or below the reference line, except for the weld symbol for field.
  • It is mandatory to use the reference line and arrow. It is also mandatory to place use a welding symbol or the tail.
  • Not all elements of a weld symbol need to be indicated or used, unless it is for clarity.

Learn Welding

Would you like to learn about welding? Check my Quick Welding Course.


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To make your life (and citation) easier just copy and paste the information below into your assignment or essay:

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Materials: Welding Symbols Introduction (Definition and Symbol Placement) 👨‍🏭 2022
Welding Symbols Introduction (Definition and Symbol Placement) 👨‍🏭 2022
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