McMurphy's hands are big and rough, while Harding's hands are small and soft.
It is clear that McMurphy has done a lot of manual labor in his day. He has made his living by using his hands. McMurphy, and his hands, represent the "man's man". They tend to be rougher, rowdier, and more rambunctious. They often don't have much formal education, but they have what is known as "street smarts" which has to do with learning from personal experience and having common sense.
Harding's small, soft hands represents his loss of manhood. He is an intellectual with a lot of book knowledge, but he struggles to cope in the real world due to his lack of personal experience. He is physically and emotionally weaker and suffers from a loss of identity. His wife cheats on him, and for much of the book he's a closet homosexual.