This device is the downlock mechanism for the High Gain Antenna (HGA) of the Viking ’75 Mars lander spacecraft, two of which landed successfully on Mars in 1976 (and operated for a number of years, returning the first information from the surface of Mars). The High Gain Antenna has a 30-inch diameter parabolic dish, which must be located as high as possible above the lander body for best radio coverage. However, this would have caused a prohibitive increase in the volumetric envelope of the lander during launch, cruise to Mars, and landing. The antenna was therefore folded down or stowed against the lander body until shortly after landing. The downlock mechanism restrained the antenna in its stowed configuration.