Hard Shut In Procedure & Lineup In Well Control
For a hard shut-in lineup, the choke remains closed at all times other than during a well control operation. The choke line valves are aligned such that a flow path is open to the choking system with the exception of the choke itself and one choke line valve located near the blow-out preventer BOP stack. When the hard shut-in procedure is selected for closing in the well the blow-out preventer is closed.
https://www.drillingmanual.com/hard-shut-in-procedure-while-drilling/