selection of the bounding box

I would like to select (make) a rectangle that is the same size and position as the bounding box of an irregular shape. By hand I can snap a guide to each edge and then make a rectangle. But, I'd like to find a way (key stroke, etc.) that will allow me to script the process. Seems like the numbers are all there for the transform tool. What am I missing?

Make a loose selection, then Select, Transform Selection. Adjust it as necessary.