Atticus needs to prove that Bob Ewell is left-handed because Mayella had been hit on her right side. When he writes his name, the jury sees that he is left-handed and was therefore probably the one to hit Mayella and not Tom Robinson.
While Bob Ewell is on the witness stand, Atticus asks him to write his name on a piece of paper. The reasoning behind Atticus' request is to show the jury that Bob Ewell is left-handed. The fact that Bob is left-handed is significant because it suggests that he may be responsible for the injuries inflicted upon Mayella's face. A man leading predominately with his left hand would more than likely inflict injuries to the right side of a person's face, which is exactly where Mayella's bruises were located. Also, Tom Robinson had his left hand permanently damaged in a cotton gin accident, rendering his left arm completely useless. Therefore, Tom Robinson would probably not have been able to inflict damage to the right side of Mayella's face. By proving that Bob Ewell is left-handed, Atticus implies that Bob was Mayella's attacker.
He wants to show that Ewell is left-handed. Tom's left arm was injured, and he cannot use his left hand. Mayella's right eye was blackened, as Scout observes, indicating that a left-handed man probably beat her up, which makes it likely that Ewell, not Tom, is the guilty one.
. Atticus asks Bob Ewell to write his name to show that Ewell is left-handed. This is important because Tom's left arm was injured; an accident later mentioned in chapter 18, therefore he could not use his left hand. Earlier Ewell said that he agreed with Mr. Tates claim that Mayella's right eye was blackened ‘“ I hold with everything Tate said”’ (Lee 176), indicating that a left-handed man most likely beat her up, which Mr. Ewell was proven to be. This makes it likely that Mr. Ewell, not Tom, could be the one who is guilty.
i think atticus makes Bob write his name to show everyone that he is left handed so it might of been him the one to beat up Mayella
he asked him to write out his name because he isright handed and tom is not and the bruies on her were from the right