Pool covers are implemented in the form of low or high walk-through structures with guide rails. These can be placed on both sides of the pool or just one.
The advantage of a single-rail pool enclosure is that the ground guide rails are located on only one side of the pool, so the rails do not interfere with entering or jumping into the water. However, the rails on at least one side of the pool are needed to guide the movement of the roof structure so that it does not cross when moving.