Finding a square square..

[rogxwhit]

Any engineer's square should do. The term should imply a certain tightness of tolerance.

But I always check a square after buying it.

Apart from engineer's squares, I actually have two or three combi squares that are spot on for woodworking.

 

[Fergie 307]

View attachment 138326
Cheapest Soba ones available at Axi although they don't mention that, and just marked as an 150mm engineers square for around a tenner, nicely machined and seems bang on to me.
Probably about the minimum length for any practical checking of other tools.

I have been very pleased with all the Soba items I have. Very well finished and accurate, and very reasonably priced.