Stand up straight facing a door or rail.
Hold onto the handle with both hands.
Bend your knees a little and lean back off the door, pushing your hips back behind you.
Round your back and tuck your tail bone under.
Keeping this position, side bend away from the side you would like to stretch.
You may also wish to reduce your grip, or even let go of the handle, on the opposite side you'd like to stretch.
Hold this position.