A fastener is any device that holds two or more things together. Look around you right now: you're probably wearing clothes held together by fasteners like buttons, zippers, or snaps. Your shoes might use laces, buckles, or Velcro straps. Even the pages in your notebook stay together thanks to staples or spiral binding, which are types of fasteners.

The word covers an enormous range of objects. In construction, workers use fasteners like nails, screws, and bolts to join pieces of wood or metal. Paperclips and binder clips are fasteners for organizing papers. Safety pins fasten diapers or hold torn fabric together temporarily. Engineers choose specific fasteners based on what they're joining: you wouldn't use a paperclip to build a bridge, and you wouldn't use a bolt to hold two sheets of paper together.

Some fasteners are meant to be permanent, like rivets on an airplane wing. Others, like the clasps on your backpack, open and close hundreds of times. The simple zipper alone revolutionized clothing design when it was invented, replacing dozens of tiny buttons. Next time you zip your jacket or snap your lunch box closed, you're using technology that took clever inventors years to perfect.