for insuring a full implement shock absorbing capacity in the system for a rough grading operating mode earth working and moving machines often have operating implements such as grader blades which are controlled by fluid control circuits selectively activated at the option of an operator of the machine in motor graders for example the work implement consists of a blade which is used in basically two different operating modes one for rough grading and the other for fine grading in the fine grading mode the blade or implement is maintained in a fixed position whereas in the rough grading mode the system preferably includes means to absorb the shocks which result from the implement or blade encountering hard immovable objects such as rocks which might be embedded in the soil the grader blade for earth working or grading machines is normally maintained in the fixed position fine grading mode for relatively long periods of time to produce a level road surface to accomplish and maintain accurate blade positioning the control system for the grader blade normally includes lock valves in the fluid circuit for the blade lift jacks which control blade elevation such lock valves are normally positioned between a control valve and the corresponding lift jack.