Tapihritsa & Gyerpung Nangzher Lodpo 
The Twenty-One Nails [EPUB ebook] 
According to the Zhang Zhung Oral Transmission Lineage of Bon Dzogchen

The Twenty One Nails is the companion teaching to the Six Lamps. It is designed to ’nail‘ the realizations of twenty one perspectives on the natural state, such as cutting through delusion and purifying mistakes of practice; establishing the path of dharmadhatu exhaustion; recognizing awakened awareness, the universal ground, the three-fold embodiment of enlightenment, the pure realms of the sacred mandala as right here, and the five primordial wisdoms; and developing the full measure of stable enlightenment. The translation includes the root text teachings transmitted from Tapihritsa to Gyerpung Nangzher Lodpo, as well as a detailed explanatory auto-commentary by Gyerpung Nangzher Lodpo.