Why Do Tape Dispensers Have Serrated Teeth?
When sealing an envelope or wrapping a package, you unroll a length of clear tape from its dispenser. You stretch it taut and press it against the row of small, pointed teeth along the front edge. Th…
Why Do Trash Cans Have Foot Pedals?
When clearing a table or emptying a bin, you head to the trash can in the kitchen or office. Near the base, a flat pedal protrudes, designed for foot contact. This pedal forms part of a linked system…
Why Do Batteries Have a Bump on One End?
You slide open the back cover of a remote control or flashlight, revealing the battery compartment. You grab a few AA batteries from the drawer and insert them one by one. Each battery has markings s…
Why Do Sinks Have Overflow Holes?
Why Do Sinks Have Overflow Holes? When washing hands or dishes, a sink basin collects water from the faucet above. The water stays in the basin until released through the drain at the bottom. Look cl…
Why Do Hammers Have a Claw on One Side?
When hanging a picture or fixing a loose board, you pick up a hammer. Its solid metal head delivers the force needed to drive a nail into place. A closer look reveals the head's distinct shape: o…
Why Do Pens Have Pocket Clips?
Every day, people pick up a pen to jot down a phone number, sign a form, or sketch a reminder. Once the task is done, the pen slips easily into a shirt pocket, notebook edge, or planner cover. A deta…
