In the structural steel drawing callout Ø1.25, the Ø stands for round structural steel tubing.

Structural Steel

Structural steel is a category of steel used in the construction of buildings and structures, renowned for its high strength-to-weight ratio and versatility in forming and welding.

Callout Ø1.25

A notation in technical drawings indicating a circular feature or hole with a diameter of 1.25 units, typically in inches or millimeters.

Round Tubing

Hollow cylindrical materials, often made of metal or plastic, used in structural, fluid conveyance, or mechanical applications.