Columns are the round or square pillars, posts or poles that flank an entranceway, and a cover flange or escutcheon is a piece of metal that is used for decoration or protection. These are typically found around the base of a post or at a point where the rail ends against a solid wall.
The decorative pieces that sit atop a post on a wrought iron fence in order to cover it are called post caps. These keep debris and water from building up inside the post, and they come in a range of designs from ball style caps to less ornate ‘flat’ or ‘standard’ post caps.