Most of the world is held together by parts nobody looks at.

A bolt. A screw. A nut. A rivet. They do their job quietly, every day, in every building, bridge, car and chair around you.

This page is about those parts: how they were used in history, why they hold, why they sometimes don't, and the machines that build the world.

Follow along. First up: the Eiffel Tower and its 2,500,000 rivets.