At San Antonio he was like a man hidden in the dark.
This is a simile which means that Jack Potter feels like a criminal. Thus, he believed that “He had committed an extraordinary crime.” This statement means that Jack believes that his method of marrying is similar to the way a criminal may act. A criminal will be hidden in the dark to kill his prey. Therefore, Jack went far away from Yellow Sky to meet his bride and actually get married. He got married in a place that is figuratively hidden from his town and his friends. Second, the simile may also describe his willingness to defend his love against everything that his friends and towns people will say against it. He has a knife, according to the simile, and he is willing to use this knife “to sever any friendly duty, any form”. Unfortunately, this feeling of ease existed only while he was far away from Yellow Sky.
Potter’s mouth seemed to be merely a grave for his tongue.
This means that he was unable to speak. The tongue is usually associated with the ability to speak. The mouth is also necessarily for speaking because people move their mouth when they speak. However, Jack was unable to move his mouth to speak. The tongue just lay at rest inside his mouth. It is compared the unmoving state of a corpse inside a grave. The grave has no other purpose, but to house the corpse. Similarly, Jack’s mouth, at that time, served no other purpose but be a place where his tongue may be located.
He sat with a hand on each knee, like a man waiting in a barbershop.
This means that he is feeling a combination of being relaxed and impatient. A man in a barbershop is relaxed because he has nothing else to do. He is also impatient because he is waiting for his turn to have his hair cut. Thus, he merely sits waiting with “a hand on each knee”. This is how Jack looks like while sitting in the couch. He looks and actually is relaxed and impatient. He is relaxed because he is married. He is impatient because he has to tell his town about his marriage.
It was a heavy and muscle-bound business, as that of a man shoeing his first horse.
It means that it [fumbling a coin and giving the coin to the porter] was very difficult for Jack to do. A man shoeing a horse for the first time does not have the benefit of experience to make the task easier. This is made harder by the natural tendency of a horse to be restless and uncooperative to such tasks. This shows the level of difficulty that Jack had to endure. However, the difficulty referred to may be psychological or emotional, rather than physical.
She was a slave to hideous rites gazing at the apparitional snake.
This means that Jack’s wife is unable to move and do anything. When a slave is offered to a god or is witness to a hideous rite to appease the gods (such as gods coming in form of snakes), the slave is unable to do anything. This may be due to a combination of shock or lack of power.
He was a simple child of the earlier plains.
This means that Scratchy found it hard to adjust to the fact that Jack was already married. Like a child of the earlier plains, his knowledge about the aspect of Jack marrying a girl is very simple. Therefore, the marriage becomes a very big surprise. It involves something unfamiliar. It is like something that people will not normally see in earlier plains. Therefore, when faced with these new things, Scratch, like a simple child of the earlier plains, found it difficult to believe and adjust to them. This difficulty in adjustment caused the confusion felt by Scratchy and his inability to give proper reactions.