When I was growing up I REEEEEEALLY wanted a grappling hook. It was one of my first prop builds when I was about 7 years old. It consisted of 6-inch long nails I found in my dad's workroom. I bent them into a hook with a hammer and vice and bound them together with duct tape. A little clothes line and I was set. I went out the garage and practiced my skills on the rafters overhead. With some persistence I managed to get it hooked tight. What to do next but attempt a speedy ascension. I got about halfway up before the loose boards that my grappling hook had hooked on decided that they were not going to stay in one place. The load of lumber dislodged from the rafters and allowed me a faster than anticipated descension. As I lay flat on my back, my precious grappling hook in pieces and lumber laying around my aching body, I realized for the first time that I was not in fact, Batman.
Fast forward to today. I built this one out of found items and 1/8" steel for the blades. It's spring-loaded with retracting blades. Its heft is really satisfying. I have no plans to try to ascend a damn thing with it. But it looks wicked hanging on my shop wall.