LEGO bricks made in 1958 still fit perfectly with bricks made today.

In 1958, Godtfred Kirk Christiansen patented the stud-and-tube design. This system uses small tubes inside the brick to grip the studs on top of another brick. This creates a strong connection called clutch power.LEGO uses steel molds to shape the plastic. These molds are accurate to within 0.002 millimeters. This is about one-fiftieth the thickness of a human hair. Such high precision ensures every brick is the same size.The company replaces its molds often to prevent wear. If a mold becomes slightly larger or smaller, the bricks will not fit. Quality control teams test bricks to make sure they require the right amount of force to pull apart.More than 400 billion bricks have been made since the 1958 patent. All of these pieces use the same interlocking system. This allows builders to mix vintage sets with brand new ones without any gaps or loose fits.