A blade assembly for a golf putter includes an outer body, a pin, and a blade. The outer body is sized to fit partially within the putter shaft. The pin has a pin shaft and a pin head, each of which have a diameter, and the diameter of the pin head is greater than the diameter of the pin shaft. The blade has a channel sized to receive the pin head. In a first position, the blade extends into the outer body and the putter shaft, substantially parallel to a longitudinal axis of the putter shaft. In a second position, the outer body and pin support the blade at an angle between 15 and 165 degrees to the longitudinal axis of the putter shaft. A golfer can thus use the putter and extended blade as a pendulum and angle finder to read the break of a green.