Dalai Lama: Karmamudra

...by relying upon a karmamudra as the external condition, the yogi on the high levels of the completion stage practices is led to great bliss.

Here one relies upon one of the four types of mudra, such as the lotus like mudra who possesses all characteristics, has been matured by tantric initiation, and has a high degree of spiritual liberation. Such a consort is known as a mudra, or a Wisdom Lady. For this practice one must understand the oral teachings well and have complete control of the two principal vital energies.

One enters into sexual union with the mudra, which gives rise to the special innate bliss. This causes the vital energies to dissolve just as at the time of death, inducing the clear light of mind to arise with great strength.

This is to be performed not only at the time of controlling the life energies, but also at the time of the three higher activities.

However, this practice is extremely secret and it is not appropriate to say more here. There I will not go into greater detail.

Source

https://gnosticteachings.org/scriptures/buddhist/199-dalai-lama-karmamudra.html