Chapter 10 says the Guru can 'strike a nail over the lines of destiny.' What does this mean, and what other benefits come from serving the Sadguru?

According to Chapter 10, the phrase 'strikes a nail over the lines of destiny' signifies that a true Sadguru, like Sai Baba, has the power to change a devotee's fate (chunk 0). This profound change is possible for those who place their faith in His feet. Beyond altering destiny, the chapter enumerates other significant benefits of devoted service. It states that pure service to the Sadguru completely destroys the worldly existence (Samsara), helps devotees overcome the three types of miseries, and leads to the effortless attainment of liberation (Moksha). The Guru is described as a boatman who safely guides followers across the ocean of existence, bestowing Knowledge (Samvitti) upon those with sincere devotion and faith (chunk 1).