Apollo–Soyuz Test Project
The docking mechanism of the Apollo was a "probe and drogue" system designed to allow the Apollo Command/Service Module (CSM) to dock with the Apollo Lunar Module. The same system was later used for the Skylab 2, Skylab 3 and Skylab 4 CSMs to dock with the Skylab space station, and the Apollo–Soyuz Test Project CSM to dock with a Docking Module adapter which allowed docking with the Soyuz 19 spacecraft. There were 12 hard latches.