The deer, one male and female, in their receptive yet attentive attitude with raised heads, symbolize the audience of Shakyamuni Buddha's first teaching at the deer park of Sarnath after attaining enlightenment. He preached the eight-fold path towards liberation from the suffering of unenlightened life. The deer would have flanked an eight-spoked wheel of Dharma, symbolizing the Buddhist teaching or 'Turning of the Wheel', and is generally placed above the front gate of a Buddhist monastery, allowing for the path toward liberation and happiness to progress.
For another pair, see R. Thurman and D. Weldon, Sacred Symbols, The Ritual Art of Tibet, 1999, cat. no. 1.