Good day.
I am still at it lol
What would be the best way to fix the fillet in the corner?
attached pic and file

Tnx!

Hi Matadem, it looks like the opening there is because these 2 pieces are separate objects and not joined together:





If you join those together so they are connected then fillet will be able to trim the upper surface instead of opening up a hole.

I've attached a fixed version that is joined, if you repeat the fillet here you shouldn't get that hole:





- Michael