Easiest way I've found is:
- Create a square via the CreateSquare[0] icon
- Put the lines as construction line
- Constrain the holes to the corners of the square.
- Add an angle constraint on one side of the square as you need.
It's easier than constraining your holes on a rectangle on which you have to replace the horizontal and vertical constrains afterwards. And you get to keep all those parametric variables that make changing something afterwards so easy.