The Hopkinsons® Uniflow valve is an adoption of the parallel slide valve principle using only one disc, which slides over the face of the seat, where it is firmly held by fluid pressure in normal working conditions, and by a light spring when not under pressure. The valve is fully opened or closed by a half turn of the handle or hand-wheel. To prevent rotation beyond these limits, stops are incorporated in the index plate. This plate is large, clearly marked, and easy to read and can be engraved to suit foreign language requirements. No lubrication is required with this type of valve. Maintenance and the fitting of replacement parts are easily carried out as the valve can be easily dismantled without the aid of special equipment. In addition, there are no welded joints to be broken in order to gain access to the internal components.