Picket fences are characterised by vertical slats of wood that are supported by horizontal rails. The classic picket fence consists of white painted pickets, pointed at the top, forming a fence about three or four feet tall surrounding the boundaries of a suburban property. While this is the image of a picket fence in most people's minds, there are several other forms that a picket fence can take.
Decorative fences generally have spaces between the pickets that are the same size as the pickets themselves. If your pickets are five inches wide, there would be a space between each one that is also five inches wide in a decorative picket fence. This symmetry between picket and space creates a pleasing composition that effectively melds the fence with its surroundings, because the viewer can see part of what's behind the fence.
A privacy fence uses a very different design than a decorative fence, leaving no space at all between the pickets. Privacy fences are usually much taller than decorative fences so that people can't see over them. Pickets are mounted on the horizontal rails to create a solid visual barrier. Both decorative fences and privacy fences are effective at keeping pets and children in the yard. If you have a particularly agile pet or child, the privacy fence is more effective because of its greater height and solidity.
If you are building a picket fence with spaces between the pickets, it is important that you make the space small enough that a pet or child can't fit his head into the space. If the space is large enough for this, there is a risk of the pet or child getting his head stuck in the fence. Pointed pickets should have points that are slightly rounded to prevent injury should someone attempt to climb over the fence.
One of the advantages of a decorative picket fence with spaces between the pickets is that it uses far less wood than a solid fence. Given the price of wood, this can add up to substantial savings in fence costs, particularly if you are fencing in a large area. Cedar is recommended as a preferred wood for fence construction, because of its resistance to rot. Cedar is more expensive than less rot-resistant woods such as spruce and pine, increasing the amount of money you will save by creating spaces between the pickets.