I'm trying to make this part 26x12x12mm with a 12mm half hole at the top. Each side is relieved 16mm half hole 3.1mm leaving 5.8mm ridge in the middle. I did it once but now can't remember how.

I cheated and extruded a 26x24x12 with a 12mm hole in the middle, Did the 16mm x 3.1mm relief on each side and cut it in half.

I sure would like to know how to do it the right way

The attachment is part of the part I'm having trouble with.

Any help would be appreciated.

Marv