The Extended Spring Assist, Dual Swivel Arm enables side-to-side keyboard movement with its 360 degree front and rear swivels. To set keyboard height position, simply loosen the height adjustment knob. Ten pounds of spring assistance helps offset platform weight during height adjustments. Once you find a preferred position just tighten knob to hold it. Set tilt angle by using the tilt ratchet handle the same way. All Weber Knapp keyboard trays and clamps mount to this arm.