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Overall view of the forward tunnel hatch.

This is a pressure hatch, sealing the forward docking tunnel against the vacuum of space.

After the Command Module and Lunar Module have docked (providing an air-tight seal between the CM and LM docking tunnels) and astronauts need to access the LM, the Command Module Pilot equalizes the pressure in tunnel using the pressure equalization valve at center, disengages the six latch assemblies holding the hatch in place using the actuator handle on the face of the hatch, removes the hatch, collapses and removes the docking probe, and removes the LM drogue, finally gaining access to the LM upper hatch.