Excuse me, how to adjust the foot screw to center the bubble of the circular level when measuring the angle with theodolite? How the foot spiral rotates! !

Rotate the bipedal spiral with both hands in the opposite direction, and the movement direction of the air bubble is the movement direction of the left thumb, so that the air bubble is located between the bipedal spiral; Then move the third foot screw with your left hand, and the direction of the bubble movement is also the direction of the left thumb movement, so that the circular horizontal bubble is centered. Commonly known as the "left thumb method".