Steel sections explained: RHS, SHS, angle, flat & more
RHS, SHS, angle, flat and round: the common steel sections and what each is good for. A plain-English guide to choosing the right profile for gates, frames, posts and repairs — and getting it cut to size.
The NKSM Team
Fencing & steel supplies, Hallam VIC · · 2 min read
Walk into a steel yard and you are met with a wall of profiles and a language of acronyms. It is simpler than it looks. Here is what the common steel sections are, what each one is good at, and how to pick for your project.
The common sections
RHS — Rectangular Hollow Section
A hollow rectangular tube. Strong in one direction, light for its strength, and the workhorse of gates, frames, trailers and structural work. Sized by width x height x wall thickness (e.g. 50 x 25 x 2.0).
SHS — Square Hollow Section
A hollow square tube. Even strength in both directions, so it is the go-to for posts, columns, gate frames and legs. Sized by side x wall thickness (e.g. 65 x 65 x 2.0).
CHS — Circular Hollow Section
Round tube/pipe. Good in compression and torsion and easy to handle from any angle — used for posts, handrails, bollards and rollers.
Angle (equal & unequal)
An L-shaped section. Cheap, stiff along its length and easy to bolt or weld — brackets, frames, edging, lintels and general fabrication. Equal angle has two equal legs; unequal angle has one longer leg.
Flat bar
A solid flat strip. Braces, straps, brackets, base plates and repairs — anywhere you need a solid, weldable flat piece.
Round bar & square bar
Solid round or square stock for shafts, pins, stakes, balustrade infill and decorative work.
Which one do I need?
- Building a gate or frame? RHS or SHS for the frame.
- Setting a post or column? SHS or CHS.
- Making brackets, braces or a base plate? Angle or flat bar.
- Structural or load-bearing work? Get the size and thickness checked by an engineer — do not guess.
Thickness, finish and cutting
Two sections can look identical but behave very differently depending on wall thickness — thicker walls carry more load and weld up stronger. Steel also comes in different finishes: raw/black steel for painting, or galvanised for outdoor and wet jobs where rust is the enemy.
You do not have to buy a full length and cut it in the driveway, either. We cut steel to size onsite at our Hallam yard, so you can bring your measurements and take home pieces ready to weld or bolt.
Not sure what to order? Tell us what you are building and we will help you pick the right section, size and thickness.
Products in this guide
Everything you need — in stock at our Hallam yard.
Frequently asked questions
What is the difference between RHS and SHS steel?
RHS (Rectangular Hollow Section) is a hollow rectangular tube that is strong in one direction, ideal for beams, gates and frames. SHS (Square Hollow Section) is a hollow square tube with equal strength in both directions, making it the common choice for posts, columns and gate frames. Both are sized by their dimensions and wall thickness.
What steel section is best for a gate frame?
RHS or SHS is usually best for a gate frame — the hollow section gives a strong, light, weldable frame that resists sagging. The exact size and wall thickness depend on the gate width and weight; heavier or wider gates need larger, thicker sections. Ask us and we can recommend a size.
Can NKSM cut steel to size?
Yes — we cut steel to size onsite at our Hallam yard. Bring your measurements and we will cut your sections to length so they are ready to weld or bolt, which saves you cutting full lengths yourself.
Should I use galvanised or black steel?
Use galvanised steel for anything outdoors or exposed to moisture, where rust protection matters. Raw or "black" steel is fine for indoor work or where you will paint or coat it yourself. If in doubt for an outdoor job, galvanised is the safer choice.
Still have a question? Get in touch — we're happy to help.
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