Traditionally they were used to prevent rain water entering the end grain of timber poles and were a simple disk or mushroom shape. Sometimes the halyard sheave, the little wheel the rope runs around, is housed inside the finial. This had the advantage of hoisting the flag an inch or so closer to the top of the pole, as well as being easier to construct in timber poles.

With modern hollow aluminum, steel and fibreglass flagpoles, there is no end grain to protect and a simple plug will prevent rain from entering the pole. Finials are now mostly for decoration, although some types do still contain the halyard sheave.

The most popular finial shapes are spheres and the traditional mushroom. Complex shapes, points, etc., are not recommended because they can foul the flag.