Why the shape matters
A steel section's shape determines how it resists bending and twisting. The same weight of steel formed into a beam carries load very differently from a flat bar.
Choosing the right section is therefore about the job: what it spans, what it carries, and how it connects to other parts.
Angles
L-shaped sections with two legs. Equal angles have legs of the same length; unequal angles do not. They are described as leg × leg × thickness and are ideal for frames, bracing, trusses and brackets.
Channels
C- or U-shaped sections with a web and two flanges. They are stiff in one direction and easy to bolt or weld against flat surfaces, which is why they appear in purlins, chassis and machine bases.
Beams
I-sections concentrate material in the flanges, far from the centre, making them efficient at resisting bending over spans. Beam size for any load-bearing structure should come from a qualified structural engineer.
Flats, bars and hollow sections
Flats and solid bars suit detail work, grills, pins and machined parts. Pipes and square or rectangular hollow sections offer good strength with a clean profile, common in gates, railings, canopies and furniture frames.