In the legend of
牛郎织女, the Cowherd and the Weaver Girl are kept apart by the Milky Way. On
七夕, the seventh night of the seventh lunar month, magpies form
鹊桥 so the two can meet.
鹊桥相会 'meeting on the magpie bridge' describes the brief reunion of a couple who live apart, and
搭鹊桥 'to build a magpie bridge' means to play matchmaker.