A spear is a pointed top element — typically a sharp or blunted spike shape — that slips over the top of a fence picket or post. A finial is a broader category of decorative top element that can be fleur-de-lis shaped, scrolled, ball-tipped, or any other ornamental form. All spears are finials in the general sense, but not all finials are spears.
Most cast iron spears and finials are designed with a socket at the base that slides over the picket top. They are secured by welding around the base, by set screws, or by a tight friction fit depending on the design. For a professional result, the spear or finial should be welded and ground smooth before finishing.
Yes. Some jurisdictions restrict sharp spear tops on residential fences, particularly on fences adjacent to pedestrian areas or where children may be present. Ball-tipped spears — which have a small sphere at the tip — address this concern while maintaining the decorative appearance. Always confirm local ordinance requirements before specifying sharp spear tops.