different flange lengts

I have an 90 degree angle piece of sheet metal and i want to give it 2 flanges that normaly come together in a 45 degree angle. Only i want to give the flanges different heights, so the angle needs to be different. How do get this properly done?

Thanks

edit: a picture, I made this with "convert to sheet metal" but its not practical. As you can see, the horizontal flange is smaller than the vertical so the angle is smaller than 45 deg.