Even the “Value” type brands are a couple of hundread for that sort of size. You could make your own, I did it at school on a smaller scale and only needs some strips of flat bar rivited together.

A framing square as Chris suggests is another option if you google “framing square stops” you will get an idea of what can easily be made to give a positive stop like the stock of a trisquare which is easier when using with thin material. These can also be tweaked to get the blade dead square to the stops

For minimum cost with maximum accuracy … follow Pythagoras

Almost any arrangement, from a length of string to as complex as you like

… sides in the ratio 3:4:5

MichaelG.

On 3 November 2023 at 09:55 Michael Gilligan Said:

… sides in the ratio 3:4:5

The OP did ask for one made to a Standard. I guess a Greek standard from 2000 years ago, still current, is as good as any.

The 3, 4, 5 ones are really the amateur version. Professionals would use the 5, 12, 13 version as it is more accurate.

I believe the NPL uses the 8, 15, 17 one for a National Reference Standard.

Joking aside, what is good is that all the above contain a number which is a factor of the 600mm characteristic dimension in the poster’s question but have different footprints to best suit the ergonomics of the situation.

So a tri-square doesn’t have an hypotenuse

… Funny language, English !

MichaelG.

One by Facom, one by Mikron Tec (sic)

https://uk.rs-online.com/web/p/engineers-squares/2360353

https://uk.rs-online.com/web/p/engineers-squares/3048471

Hi, I made a square from an off cut of 6mm steel plate, just cut it in half and welded the two bits together, this was about 27 years ago when I was building my garage, and it’s just a little bit over 1 meter long on each leg, and it is still just as square as it was then, measuring it and by using Pythagoras, makes it no greater than 0.2mm under square.

My Frame square is 910mm by 610mm approximately, and is over fifty years old, used to use it in my old day job, when doing large fabrications, bit rusty now and the measurement marks are a bit hard to see, it has inch measurements on the other side, but is still reasonably square.

Regards Nick.

On 3 November 2023 at 13:53 Michael Gilligan Said:

So a tri-square doesn’t have an hypotenuse

… Funny language, English !

MichaelG.

Us woodworkers use a try square.

Mark.

Ah, but I’m not an expert at spelling so you should not take what I write as read when playing your word games.

Though both are used , Try is more common.

For clarity a try-square is also L shaped and a set-square triangular.

everything is made to standard sadly, most to a low one. considering what you are  using it for  a cheepie should do