How does 737 Rudder Trim knob work in real world?

How does the real 737 Rudder Trim knob operate?

Does it trim only one unit with each turn to the right or left? Or does it continuously apply trim when turned until it is released? Or does it apply more trim the farther it is turned to left or right and stop when released?

Applies trim continuously until released. Its one speed, so you most hold it for a bit if you want a lot of trim.