A strand jack is a specialized hydraulic lifting device used to move extremely heavy loads—often thousands of tons—where traditional cranes are impractical or too expensive. It was invented in 1969 by Patrick Kilkeary and Bruce Ramsay of VSL Australia, originally for concrete post-tensioning systems. The device works like a caterpillar's walk, using steel cables passing through a hollow cylinder with alternating clamps, allowing for precise, controllable movement at any speed. Multiple jacks can be operated simultaneously via computer control—up to 120 at once—enabling the tandem lifting of massive structures with fingertip precision, and they can also be used horizontally to skid heavy objects like oil rigs onto barges. Notably, strand jacks were used to erect the London Eye, lift the sunken Russian submarine Kursk, and salvage the wreck of the Costa Concordia cruise ship.