The first Patrul Rinpoche (Dza Patrul Chokyi Wangpo) was a very learned and accomplished master of the 19th century in Tibet. He wrote widely on all aspects of practice. In this text, he explains the most important foremost instruction taught in the Nyingma tradition for Development Stage practice. It is a Nyingma teaching but it is completely applicable to the Development Stage practice taught in all of the schools of Tibetan Buddhism.
The name of the foremost instruction explained in the text is Four Nails Pinning the Life-Forces. This instruction is a set of four headings which cover all the main topics of Development Stage practice and which are, at the same time, a complete set of instructions for the practice. It goes even further than that: because they are the main topics of Development Stage practice, they also include all of the many sub-topics of the practice. Patrul Rinpoche explains all of this clearly and then enumerates forty different sub-topics, each one being an instruction for Development Stage practice. Moreover, when Dza Patrul explains the Four Nails, he also explains it in terms of the other main instructions for Development Stage practice; for example, he gives an excellent explanation of the subject called Purifying, Completing, Ripening in relation to the first nail. Altogether the text is a very rich source of instruction for anyone doing Development Stage practice and an excellent resource for those trying to understand its various details.
The importance of the Four Nails instruction can be understood from the fact that, whenever authors in the Nyingma tradition need to summarize the points of Development Stage practice in one place, they refer either to the Four Nails or to the Purifying, Completing, Ripening instruction mentioned above. Because this text explains both sets of instructions it is an ideal way to learn the key points of Development Stage practice.
This teaching is also covered, but in a different way, in the Longchen Nyingthig text on deity practice, which we have also published, called A Presentation of Instructions for the Development Stage Deity; you will want to read both books together.
To the best of our knowledge this is the first time that a clear instruction on the Four Nails and Purifying, Completing, Ripening instructions has been translated and published. The Tibetan text, from the Derge Edition of Dza Patrul's Collected Works is unclear in many places and has a number of mistakes in it. Lama Tony carefully edited the text to repair it, then included it in the book with the thought that students could take the book to their teachers and ask for instruction on it. We think the book will be quite useful and popular in this regard.