Quick answer

The horizontal fillet (2F) is one of the most common welds in fabrication. In short: clean; tack; hold, then complete the remaining steps below.

Step by step

Clean mill scale, rust and oil from both pieces and fit them tightly at 90 degrees.
Tack weld the joint at each end.
Hold the gun at about 45 degrees between the plates, with a slight 10–15 degree push or drag angle per the process.
Strike the arc and establish a puddle at the root of the joint.
Travel at a steady speed, keeping the wire aimed slightly toward the bottom plate.
Watch that both toes of the weld wet into the base metal without undercut.
Clean and inspect the weld for size, profile and defects.

Safety reminders for welders

Wear a properly shaded welding helmet, flame-resistant clothing and gloves
Use ventilation or fume extraction, especially for stainless and galvanized steel
Follow hot work permits and keep a fire watch where required
Secure gas cylinders upright and away from heat

SMAW (stick) · GMAW (MIG) · FCAW (flux-core) · GTAW (TIG) · Bead · Weld puddle: see the full welder glossary.