The Square Guide

The set square is used to ensure the accuracy of layout lines and cuts made with other tools. It must always be accurate because otherwise subsequent work will result in lower levels of work quality.


The set square is one of the most important tools used in making furniture. It is used for marking out right angles before any joint is cut. It can also be used for marking straight lines and checking straight edges. The tool is often used alongside other tools such as the layout knife. The square and layout knife combined are regularly used to create very precise lines to cut to.


A square is made up of two parts, the beam and the head (or ‘stock’). The beam is a thin blade of steel and the head can be made from metal or wood and is heavy. The beam is 90° from the head and is used to check right angles. On a combination square the beam has measurements on it and also has a head with a 45° aspect to it as well as 90°.

Types of Squares

The two most commonly used types of square are the combination square and the try (tri) square. The main difference is that the combination square has a head which can be moved along the beam whereas it remains in a fixed position at 90° on the try square.

Parts of a Square

● Beam

● Head (Stock)

● Locking Screw

Relevant Guides

  • Setting Up a Square

    Setting Up a Square

    To check if your square is accurate, you can use a piece of paper or card stock as, due to their manufacturing techniques, they are very accurately square. Put your square on the long side of the paper and draw down one side of the beam, either using a knife or a sharp pencil. Then…

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  • Using a Combination Square

    Using a Combination Square

    Once you are confident your square is set up you align the head (stock) against the straight edge of the wood and use a pencil or a woodworker’s knife to mark the 45/90° angle. To move the head along the beam, turn the adjustment wheel to loosen the head, this enables it to be moved, when…

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  • Buying a Square

    Buying a Square

    Paul Sellers recommends a 12″ (300mm) combination square as this should be suitable for almost all woodworking projects. He finds the try squares don’t remain accurately square as with the better quality combination square. When buying a square, look out for one with a cast iron head as the ones with aluminium heads tend to…

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Further Reading

To read more on this we recommend the following from Paul’s blog:

On Woodworking Squares and Working Wood

My Minimalist Tool List- The Square

Buying Good Tools Cheap #2- The Combination Square

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