Bay 2 workers observe the movement of the airlock as it is lowered into Endeavour's payload bay for installation.

In Orbiter Processing Facility bay 2 at NASA's Kennedy Space Center, workers observe the movement of the airlock as it is lowered into Endeavour's payload bay for installation. The airlock is located in the middeck. The airlock and airlock hatches permit flight crew members to transfer from the middeck crew compartment into the payload bay for extravehicular activities in their space suits without depressurizing the orbiter crew cabin. The airlock is sized to accommodate two fully suited flight crew members simultaneously. Photo credit: NASA/Jim Grossmann