How to read welding symbols on a blueprint?

Standardized welding symbols (CSA W59 / AWS A2.4 standard) precisely indicate on a blueprint how a weld should be executed:

Symbol structure:

• Reference line: Main horizontal line
• Arrow: Points to the joint to be welded
• Tail: Optional, contains additional information (process, specifications)

Elements on the reference line:

• Above the line (other side): Weld type symbol for the side opposite the arrow
• Below the line (arrow side): Symbol for the side the arrow points to
• Example: Fillet weld symbol (right triangle) below the line means fillet weld on the arrow side

Additional information:

• Size (left of symbol): Example: ¼ means ¼ in (6 mm) fillet weld
• Length (right of symbol): Example: 3 means a 3 in (75 mm) long weld
• Pitch (spacing): Example: 3-6 means 3 in weld every 6 in
• Tail: Example: SMAW (process to use)