Sadly, neither suggestion gives the intended result. I maybe should have mentioned this before, but I want the inner corner to be 'negative' (270), and the suggested method seems to give me a positive 90-degree angle. Any more bright ideas?

thanks,
Niels

I'm sure that Inkscape can do the following; I ust can't figure out how to get there. What I need is a rectangle, one quarter missing, and all corners rounded (let's say an L-shaped box; by the way, does this shape have an English name?). The shape is easy enough to create with a boolean 'difference...