The following paragraph is from Don Winslow's novel The Force:
Malone and Russo and Billy O and Big Monty and the rest made these streets their own, and they ruled them like kings. They made them safe and kept them safe for the decent people trying to make lives there, and that was their job and their passion and their love, and if that meant they worked the corners of the plate and put a little something extra on the ball now and then, that’s what they did.
I can guess that "worked the corners of the plate" and "put a little something extra on the ball" are baseball idioms and these two probably mean doing something unscrupulous or cheating. But I don't watch baseball and I have a hard time understanding why and how "working the corners of the plate" would indicate dishonesty.