These aren't offered as decent photographs, but just as a record of what seems to be a sort of art (or film) project worked out on the Humanities Building, here at the University of Wisconsin-Madison.
At the area at the top, where there is a pedestrian walkway, there are fake sandbags piled up. Behind the "sandbags" is some sort of (fake) mortar firing device. In front of them, on the sloping wall, is a fake mortar sort of thing, given the appearance of penetrating into the building. There are various chalk markings on the wall to make it look as if there had been an attack. I have no idea what the point of this is. I just saw it and photographed it. As you make your interpretations, take into account that there have been various fool-the-eye chalk drawings on this building, which houses the art school.
IN THE COMMENTS: Is that a mortar or a rocket? Those who seem to know say rocket. I realize I don't know the difference. And I did try to figure it out before posting, so it just goes to show that you can't get all your answers from the internet. But I did find this book, a fun book for kids, which contains instructions for making a "tennis ball mortar," which involves PVC tubing and lighter fluid in a tennis ball. I love the instructions, which tells you to be very careful, be sure to have adult supervision, and know that there is absolutely no way you can sue the author or publisher.