flagpole

A flagpole can serve as the benchmark for a structure's tip height when the highest point on the structure is a narrow mast designed to hold a flag. The flag itself is not measured in the tip height, nor is the rope securing the flag, because it does not have a constant height.

The mast provides a fixed upper point even while the flag changes position. The variable height of the flag or rope does not extend that measured tip.

A flagpole standing below another higher element does not supply the structure's highest point. Its tip-height role depends on the mast itself being uppermost.