Nonmeditation is the essential unique method of Dzogchen meditation. But nonmeditation cannot be programmed or devised. These twenty-one semdzins are open-sesame keys to nonmeditation, meditations that open up into nonmeditation or make space for nonmeditation. The natural flow of consciousness is dammed by the semdzin and mind is 'held' momentarily, during which time the window to the nature of mind is thrown open or enlarged and nonmeditation can proceed at a high level. Certainly, a powerful head of energy is built up behind the dam of semdzin discipline and particular mind-states may be engendered such as high awareness with varying degrees of bliss, radiance, thoughtlessness and emptiness. Longchen Rabjampa collected these twenty-one semdzins in the 14th century. They may be understood as separate but equal, all valid in their own right, or they may be categorized, as they are herein, according to three graduated functions. Those three are pacifying the mind, releasing attachment and revealing the nature of mind. Many of these exercises may be found in mahayana and some even in hinayana sources, the difference is that in the lesser modes a temporal goal is anticipated, whereas in Dzogchen, in every case, a nondual refuge is the outcome. These exercises are not to be practiced in a period of temporal sadhana, but it is advisable perhaps to undertake a short retreat or period of intense engagement with each of them, several of them or one of them to gain familiarity. These practices are disseminated for the benefit of Dzogchen nonmeditators. For each Semdzin, Longchenpa's highly practical instruction in English and Tibetan is followed by comments from Namkhai Norbu and a commentary from Keith Dowman. 80 pages.