TSO products makes that guiderailsquare for festool. TSO offers an "angle accessory" that mounts to those holes, so you can use the square more easily on material with rounded/profiled corners.
[member=76969]Paulw6969[/member] - the holes in our GRS-16 PE (licensed by TSO to FESTOOL and offered as their FS-WA/90) are universal SYstem accessory mounting Holes M6 100mm on center.