How the Modern LEGO Brick Design Works

The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly.

What it covers

This patent describes the structural design of a toy building brick that features hollow cylindrical tubes on its underside. These tubes are positioned to frictionally engage the walls of other bricks when pressed together. This specific arrangement allows for a stable, interlocking connection that remains secure even when the structure is moved or turned upside down. It transformed simple plastic blocks into a versatile construction system.

What it doesn't cover

• —Does not cover bricks without the specific hollow tube configuration on the underside
• —Does not cover non-plastic materials or different geometric shapes like spheres or pyramids
• —Does not cover the specific chemical composition of the plastic used

The clever bit

The innovation was placing hollow tubes inside the brick to create a friction-fit with the studs above, rather than relying on simple gravity or loose stacking.

Why it matters

This design is the foundation of the entire LEGO brand. By solving the problem of structural instability in early plastic blocks, it enabled the creation of complex, multi-story models that do not fall apart during play.

Real-world examples

• 1.Standard 2x4 LEGO bricks
• 2.LEGO Technic beams
• 3.LEGO Duplo blocks