Which Invention Is Very Useful And Very Simple?

Dolos are tetrapod-shaped concrete or quarry rock breakwaters, useful for protecting shorelines from the erosive force of water.

The specific configuration allows water to flow around rather than against the concrete and reduces displacement by interlocking.

A dolos (plural dolosse) is an unusually shaped concrete block weighing up to 20 tons which is used in great numbers to protect harbour walls from the force of the sea. They were developed in East London, a port city in South Africa, in 1963 and are found in their millions around the world.

Invented by Aubrey Kruger and later designed by engineer Eric Merrifield, their design is not protected by any form of patent. Both felt it was unnecessary to register their rights as they considered their invention to be a benefit to mankind.