Reminds me of a nasty injury at work, back in the early 1980s.
The early GEC minicomputers were constructed in deep drawer units on runners (we called them "crates") in 19" racks. The backplane was on the bottom, with the cards plugging in from the top when the crate was pulled out on its runners. A metal lid and identical bottom plate screwed on to channel the airflow correctly, although these systems were so over-engineered that it didn't matter if they were left off, so they often were left off on the engineering development systems in the lab.
The backplanes were made using a large PCB with through plated holes which had wirewrap backplane connectors connected by being forced through the tight fitting holes. They weren't soldered, just very tight fit with the sharp square edged pins cutting into the through hole plating. Much to my surprise they were incredibly reliable - I don't recall any failure in 20 years.
One of the engineers was working on a couple of crates, one at the top and one at the bottom of a 6' rack. Now you're thinking with two crates extended, he managed to tip over the rack - no, they had sodding great weights in the base of the rack to prevent that. However, when he finished working in the bottom rack, he slid it back in and stood up. Normally, he would have just banged his head on the top crate, having forgotten it was pulled out. However, the bottom cover was missing, so as he stood up, he managed to plug his head into many hundreds of wirewrap pins sticking out the bottom of the backplane. I wasn't there, but apparently blood instantly came pouring down his face and neck like as waterfall, and he promptly collapsed. He was OK in the end though.