Yowch! I once bent down to pick something up at a former job, and stood up and slammed my head on an old valve sticking out from a pipe. I hit it so hard, they made me go to the hospital to check for a concussion. I didn't have one, just a big bump and bruise. I chalk that up to one of the benefits of being a fershlugginger hard-headed Swede! But by the time I got back, the maintenance staff had painted it BRIGHT blue - so no one could miss it, and it wouldn't happen again!