The association or connection between master and disciple is particularly important. This association leads to the formation of lineage. Lineage is, of course, important not only in the Vajrayana but also in the Buddhist tradition as a whole, especially when it comes to monastic ordination. If you look at the history of monasticism in Sri Lanka and Thailand, you will notice the importance accorded to it. Because of discontinuation of the lineage of monastic ordination, special envoys had to be sent from one Theravada country to another on a number of occasions, simply to renew the lineage.
Lineage is like an electric circuit.
When the lineage is broken, the ordination of new disciples cannot take place. Thus lineage is extremely important. The concept of lineage implies the identity of each link in the chain, each member of the lineage. Consequently, the figure of the preceptor secures identification between the master, disciple, and tutelary deity. Later, the disciple him or herself forges this bond as he or she develops his or her own sense of identification with the preceptor and then with the tutelary deity.