A paper machine carefully removes water from the paper sheet. Some of this water removal is done by passing air through the sheet, thus moving the water from the sheet to the wire. Air is moved by creating a pressure differential across the sheet. This is normally done by putting the sheet on a wire and then putting a box under the wire and then evacuating the air from the box. The resistance of the air movement through the sheet and wire causes the pressure drop from the machine room to the box.