The displacement device serves to hold a separation element, which is pivotally connected to a bracket, which is held slideably by a first beam of a scissor assembly and firmly by a second beam of the scissor assembly with a scissor assembly bearing. Maintenance and control of the sub atmospheric pressure exerted may be provided by such devices while minimizing discomfort to the user. The access level reflects the proficiency level of the user, such as novice, intermediate or advanced. A contact electrically connects the lower electrode and the upper interconnection. The communication between the inlet reservoir and main reservoir consists of plurality of ports distributed circumferentially each port being provided with a check valve. The device is in the form of a straight hollow cylinder with one of the bases being either the wall of the device or being in contact with the wall of the device.