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 go out of square after a while and are difficult make square again. If you cannot get one with a cast iron head, just make sure you check that it is square before starting each project. The ones with a cast aluminium head can be found for under £10, the ones with a cast iron head are more expensive and can be bought between £25-30 and on up to over £100.
To view the parts of a square, click here.
We purchased this combination square from Amazon Prime for £21.99*
*Prices correct as of June 2018
To read more on Squares, we recommend the following from Paul’s blog: