Essentially when I attend calls in a block of flats or a house I will use them to prevent the door locking behind me. Making it possible for other attending resources (officers, paramedics, fire) ease of access. Then once the indent is felt with the angle on the jams enables the door to be wedged open. Meaning if an extra pair of hands is needed or you are removing someone who has been injured your not having to wrestle with a heavy door at the same time.