Hand crank table base lift mechanism features two 2.5 ton rated screw mechanisms that is the height adjusts from 10″ – 18″, this piece has a 10″ cast iron wheel, crank the wheel and it goes up or down. Can be built in many sizes as a desk or table. Or two larger 5 ton rated screw mechanisms that support and adjust the top height (30″ to 42″), as well as two 12″ cast iron crank handles. Turn either crank handle to raise or lower the top. Or this table uses four 2.5 ton crank mechanisms with a combination of gears and heavy duty industrial parts to adjust the height from 30″ to 42″.