Air terminals used for lightning protection exceeding 24 in. in height shall be supported at a point not less than __________ of their height.

The requirement for supporting air terminals used for lightning protection is that if their height exceeds 24 inches, they must be anchored at a point not less than half of their overall height. This design consideration is crucial for ensuring stability and strength against the forces that may act on the terminal during a lightning strike or during severe weather. Supporting these terminals at this specified height provides a balance between structural integrity and flexibility, reducing the risk of failure during extreme conditions.

The reasoning behind the "half of their height" requirement is fundamentally related to engineering principles regarding load distribution and stress. By anchoring at this level, it helps to ensure that the terminal is adequately stabilized while still allowing for some movement to dissipate energy more effectively in the event of a lightning incident.