To fall in line literally means to stand in front of someone else in order to form a line. The idiom fall in line means to follow the rules or codes of behaviour that are expected by others. To fall in line means to conform and behave like everyone else and follow the status quo.

1. Henry was asked to redo the work he submitted because it did not fall in line with his boss's expectations. 
2. If I can convince just one of the business people present to invest in my product, I believe the others will fall in line.
3. Despite talk of strike action, Teachers are expected to fall in line with the controversial new regulations.

1. Henry was asked to redo the work he submitted because it did not fall in line with his boss's expectations. 
2. If I can convince just one of the business people present to invest in my product, I believe the others will fall in line.
3. Despite talk of strike action, Teachers are expected to fall in line with the controversial new regulations.