These are normally used in hydro-elecric high head tunnels where a the use of a wheel or roller gate design is not practical, can be used to control the flow through the tunnel.
Advantages
Can be used for very high heads up to 200m
Side groove sizes can be kept to a minimum to reduce flow disturbance.
Sealing faces are metal to metal slides.
Can be rectangular or circular bore.
Normally configured as Service + Guard gates for maintenance
