The book says the Guru can 'strike a nail over the lines of destiny.' What does that mean and how else does he help his followers according to Chapter 10?

According to Chapter 10, the phrase 'strikes a nail over the lines of destiny' means that the Sadguru has the power to change a devotee's fate. The chapter elaborates on this by explaining that through faith and pure service, the Guru helps devotees overcome immense obstacles. He is described as a boatman who helps his followers cross the 'ocean of existence' (Bhavasagar) and the three types of miseries. Furthermore, by the Guru's mere sight, the knots of the heart are broken, attachments to worldly objects vanish, and both accumulated (Sanchit) and current (Kriyaman) karmas are destroyed, leading the devotee effortlessly toward liberation (Moksha).