Tip: As you edit the rectangle, datum planes display to indicate the original shape and size of the wall. If the lines you sketch snap to the datum planes, the endpoints of the lines automatically align to the planes, unless you explicitly unlock them. If you unlock the sketched lines, you can modify them independently of the datum planes. If you exit sketch mode while the sketched lines are still aligned, as you move a datum handle, the sketched lines move with it.
Sketch lines unlocked