In John Steinbeck's The Grapes of Wrath, of what are the ‘soft’ and ‘hard’ fingers symbolic?

There's sort of an old truism about the distinction between those who earn their living performing manual labor and those who sit at desks and stare at computer screens, or perform other types of "white collar" work. Look at a man's hands, and you can tell into which category he belongs. In John Steinbeck's classic novel of the depression and the "Dust Bowl" migrations from the Midwest to the Far West, The Grapes of Wrath, that distinction plays a major role. Steinbeck's protagonists, and heroes, are the victims of economic changes, faulty management, and natural disasters. They are also honorable, hard-working people struggling to support their families during the hardest of times.

Early in his novel, and especially in Chapter 5, Steinbeck emphasizes the physical characteristics of his honorable, hard-working people. He does so, in part, by reference to their hands. Twice in these early chapters he uses the analogy of clam shells to illustrate the hardness and coarseness of hands spent performing back-breaking work in fields and factories, as in the following passage from Chapter 2:

"His hands were hard, with broad fingers and nails as thick and ridged as little clam shells. The space between thumb and forefinger and the hams of his hands were shiny with callus."

Later, in Chapter 8, the author again uses the clam shell metaphor to emphasize the difficult life of his main character, Tom Joad:

Tom's heavy lips were pulled right over his teeth. He looked down at his big flat hands. "No," he said. "I ain't like that." He paused and studied the broken nails, which were ridged like clam shells. "All the time in stir I kep' away from stuff like that. I ain' so mad."

The softness or hardness of a man's hands were indicative of his status in society and of his proclivity for being victimized by those higher up that socioeconomic ladder. Which brings us to Chapter 5. In this chapter, Steinbeck depicts a discussion between those who own the farms, ranches and businesses, and those who perform the manual labor necessary for the company's or farm's success. In this scene, "owner men" are discussing the situation with the migrant workers, like the Joads, whose survival are dependent upon these men. The owner men sit in their cars and converse with "the squatting tenant men praying for work so they can support themselves and their families. Note in the following sentence from Chapter 5 Steinbeck's use of these men's hands to distinguish between the haves and have-nots:

Soft fingers began to tap the sill of the car window, and hard fingers tightened on the restless drawing sticks.

The "owner men" are sitting in their cars, their hands soft from enjoying the luxury of paying other men to perform the manual labor. The "tenant men," in contrast, are squatting on the hard ground, holding sticks they use to illustrate their points by drawing in the dirt. The hard and soft fingers or hands are symbolic of the relative status of the characters in The Grapes of Wrath.