It is a deputy handle. In order to meet the requirements of man-machine courses, it is slightly chicken ribs.

When the electric drill is in use, one hand may not be able to grasp the balance sometimes, and one hand is fatigued quickly, so the extra auxiliary handle can be used by the other hand to maintain the balance and stability of the electric drill, thus ensuring the safety. The other auxiliary handle can decompose the gravity of the electric drill itself and relieve the fatigue of one hand, which is not the existence of chicken ribs in theory. I just didn't understand how the author's deputy handle was rotated and fixed at 360 degrees.