How deep must a lawn edging stone be embedded in concrete?

I also point out that if the wedge holding the Tiefboard is too close to the turf, it dries out too quickly in summer.

That means you would "grout" between paving stones, gravel, etc.?

If you use lawn edging stones and belong to the people who like "cleanliness and order" in the garden, do as recommended.

If you prefer a natural edge without taking up more space, a simple solution is available: untreated thick wooden planks held in place by iron rods driven deep into the ground. The planks will rot away picturesquely over the next 15 years, leaving a naturally stable structure.

and why does something like that hold?

it's not like the mountain is pressing directly against it, but there is still a 40cm wide path in between and behind that there are supporting rubble stones

Because deep enough in the concrete therefore just that.

Because deep enough in the concrete, that's why.

I strongly assume that these are just standard curbs, of which 10-20cm stick out easily. I assume this because I have seen such pictures often and, according to the description, lawn edging stones were often used. And apparently, they don't come in sizes larger than 40cm high. So either a) I'm mistaken b) people lie in their construction blogs c) setting half of the stone in concrete is sufficient d) there are indeed larger curbs and neither the nearby hardware stores nor the building material suppliers know about them