Abstract: A jack-up unit for use in a body of water, said unit comprising a floatable hull, a plurality of legs, said legs being suitable for contacting a solid surface and for supporting said hull in an elevated position relative to the surface of said body of water, each of said legs including at least one longitudinally extending leg gear rack, means for moving said hull longitudinally relative to said legs for establishing said hull at a desired height relative to said legs, a guidance system on each leg comprising an upper guide member configurative around said leg at a close tolerance interval and a lower guide member configurative around said leg at a close tolerance level, and a plurality of gear rack sections located one proximate each leg intermediate said upper guide member and said lower guide member, each gear rack section moveable into and out of toothed engagement with said leg gear rack section on its respective leg, said toothed engagement including a gear tooth backlash in excess of said close toleran