Span shades are a type of shade structure that include usually four (sometimes more) upright columns in a set spacing with steel rafters connected to an over-head cross piece. The advantage of span shade structures is that they enable you to achieve a substantial area of shade, on a minimum number of supporting columns. This can be great in areas where upright posts may cause an obstruction or be considered unsightly.
Additional advantages of span shade structures is the design of the canopy; with the highest point of the canopy being in the middle. This enables greater height clearance over objects such as play equipment, seating areas etc. This also means that the lowest part of the canopy is around the perimeter, providing better shade coverage for more of the day.