The gyro is initially erected using a caging mechanism, which manually places the gyro spin axis
in its horizontal plane. The mechanism consists of a bevel pinion and a caging arm, which are
both directly controlled by a caging or setting knob sited on the front of the instrument. By pushing
the knob in, the bevel pinion engages with the synchroniser gear ring, and it allows the scale to
adjust in azimuth by rotating the caging knob. At the same time the caging arm is raised, which
locks the inner gimbal ring in its horizontal plane, and prevents the gimbal ring and rotor from
toppling during resetting. The caging knob is pulled out to uncage the gyroscope, by disengaging
the gears, and allowing the caging arm to drop, thus releasing the inner gimbal ring. The inner
gimbal should also be locked in its horizontal position during aerobatics, to prevent severe loads
being transmitted to the rotor bearings.