When a screw sticks out on metal or isn't perfectly flush with the surface, an angel in heaven loses an eyeball. Or something like that. But fret not eyeballs of angels in heaven, people of Earth can make a screw completely flush. It's a lot of filing and sanding and hammering but eventually the screw disappears.
If you've ever struggled to keep your drinks in their receptacle at the beach, this concept will have your pretty excited: Screw Cup is a mug that can be driven into the ground to help it stay upright.
Many kinds of human engineering have biological equivalents - the most famous is probably the ball and socket joint, which is found in car steering columns and human arms alike. The newest and weirdest example is insects with screw-and-nut legs.
Earlier there was worry that Apple's freaky "pentalobe security screws" would prevent us from opening up our iPhones. Turns out that we're only $2.35 (plus shipping!) away from tampering with our gadgets again thanks to a wholesaler.