Picket caps (vinyl)
Vinyl picket fences are built with smaller vinyl fence components acting as the pickets, but because vinyl fence is extruded, and those sections are hollow, they need something to close the top of the picket and create the familiar shape of a picket fence.
The solution is what is known as a picket cap, which is a specially designed vinyl fence cap that fits inside the vinyl fence picket, held in place by a ridge along the bottom of the picket and usually pressure clips.
Vinyl picket caps come in a variety of colors and sizes, so you can build a vinyl picket fence from most colors of vinyl fence material.
Buy vinyl fence picket caps on Amazon