Abstract: A rodless cylinder consisting of a cylinder, a piston within the cylinder for reciprocal movement therein, a guide along the outside of the cylinder, a drive block mechanism constrained to move along the guide, a pulley at each end of the cylinder and guide, a cable extending from each end of the cylinder, around a respective pulley and secured to a respective end of the drive block mechanism, a compressible resilient member extending from each end of the piston and, a sealing member co-operable with a valve seat located within an exit from each end of the cylinder, such that when the piston approaches one end of the cylinder, the resilient member forces the sealing member into sealing contact with the valve seat so preventing egress of fluid from one end of the piston to the outside of the respective end of the cylinder. The pulleys, cables and cylinder are also completely enclosed so that only the top of the drive block is exposed to the outside environment.