Combination Squares, Centre Heads and Layout Sets

Combination squares measure, mark and check 90° and 45° relationships for carpentry, fabrication, machining, fitting and workshop inspection. A sliding rule and locking head allow one tool to check squareness, transfer dimensions, gauge depth and mark parallel lines. Multi-head sets add centre-finding and variable-angle functions.

Choose the rule length and graduations

• 150 mm rules: remain compact for bench, trim and confined layout work.
• 300 mm rules: provide a practical general-purpose range for workshop and site tasks.
• 400–600 mm and longer rules: cover larger components but require a sufficiently flat reference surface and careful handling.
• Metric, imperial or dual scales: should match the drawing, inspection method and units used on the job.

Select the head configuration

A standard square head provides 90° and 45° reference faces and may include a spirit vial or scriber. Centre heads locate the centre of compatible round stock. Protractor heads provide adjustable angle layout. Multi-head sets are useful when those functions are required, but confirm exactly which heads, rule and accessories are included.

Construction and compatibility

Compare cast iron, metal-alloy and high-impact head construction, rule material, etched graduations, locking mechanism and reference-face finish. Replacement rules, heads, scribers and vials are not universally interchangeable. Match accessories to the manufacturer and model series before purchase.

Checking and accurate use

• Clean the rule, head channel, reference faces and workpiece before use.
• Lock the head without excessive force and make sure it does not shift during marking.
• Check squareness against a known reference or by reversing the tool against the same straight edge.
• Use a suitable marking tool and light pressure so the rule or head is not displaced.
• For documented inspection, confirm the stated accuracy and any calibration or certification supplied with the exact SKU.

Browse Chalk Lines & Refills, Rulers & Straight Edges and Hand Tools for related layout equipment. Confirm rule length, graduation system, head material, included heads, accuracy and accessory compatibility on the product page.

Combination squares from stocked trade brands

Compare squares and layout sets from Starrett, Kincrome, OX Tools, Bahco, Groz, Toledo, Spear & Jackson, Sterling, Trax and Precision Specialty Tools. Availability varies across standard, cast-head, multi-head and replacement-component formats.

Combination square FAQs

What size combination square is best for general work?

A 300 mm model is a common general-purpose choice, while shorter or longer rules suit specific access and component sizes.

How can I check whether a square is still square?

Use a verified reference or draw a line against a straight edge, reverse the square and compare the second line.

Can I fit any replacement rule into any head?

No. Dimensions, locking grooves and graduations vary, so confirm compatibility with the exact model.

Does every combination square include certification?

No. Check the individual product for stated accuracy, calibration or certification where documented inspection is required.

Industrial Shed support

Industrial Shed provides Australia-wide shipping, Mornington Peninsula local delivery, in-store pickup and measuring-tool support through its trade services.