Create a rounded box with two square corners
 

I keep trying to create a box with only two rounded corners. I have tried making the points editable and dragging the handles into the point but it still doesn't create a true squared corner.

Is there no way to convert a curve point to a corner point like in Illustrator?

The easiest solution is to create a rounded box, and a square box, and merge the two, using Edit: Shapes: Union Shapes.

There's a shape that matches this description in the Shapes stencil. Hope that helps.

The above options are good, or if you want to do it your way then there's a simple solution - I'm guessing you don't work with vectors often, which is fine :)

On the end you want to be square, delete one point from each corner, then just level out the curve. Done.