A picket fence runs vertical pickets between a top and a bottom rail. Pickets can be flat bar (most traditional), square tube, or round tube, in aluminium or steel. The structure reads as light and open compared to slatted or battened panels. The same look in timber is the most common 'cottage' fence in Australia.
Steel picket fence, usually flat bar, is the traditional choice for schools, parks, and heritage residential areas where the look is meant to reference wrought iron; aluminium picket fence is the lower-maintenance modern equivalent. Picket spacing varies but tends to run 80 to 120 mm between picket faces. Tighter spacing pushes the look toward a tubular fence; wider spacing pushes it toward an estate-railing look.
Not pool-compliant unless the picket spacing is 100 mm or less and the top rail is non-climbable from outside.