This valve is typically utilized in dilute phase pressure or vacuum systems or under atmospheric (gravity) conditions. This valve gets its name due to the fact that the slide plate has an orifice (opening) that, when the valve is opened, aligns with the openings in the top and bottom valve frame openings. It utilizes dynamically loaded polymer seals (pressures plates) and provides positive material and air flow shut off up to 15 PSIG. Optional valve features can be added for use in fine, sticky, or packable material applications.