Cash Explains the Bevel — As I Lay Dying

I made it on the bevel, Cash says. There is more surface for the nails to grip. There is twice the gripping-surface to each seam. The water will have to seep into it on a slant. Water moves easiest up and down or straight across, and Cash has thought about water the way other people think about feelings.

In a house people are upright two-thirds of the time, so the seams and joints are made up-and-down because the stress is up-and-down. In a bed where people lie down all the time, the joints and seams are made sideways, because the stress is sideways. Except. A body is not square like a crosstie. Animal magnetism. The animal magnetism of a dead body makes the stress come slanting, so the seams and joints of a coffin are made on the bevel.

You can see by an old grave that the earth sinks down on the bevel, while in a natural hole it sinks by the centre, the stress being up-and-down. So I made it on the bevel. It makes a neater job. He never names his mother. He never says he is heartbroken. What does a person mean when the only love poem they trust is a list of nail grip and grave earth?