Slatted covers are made from interlocking PVC or Polycarbonate. They can be installed in pools either underwater, or on an above-ground roller, resting on the water’s surface and relying on the pool’s natural physical properties to float. They can be opened and closed using a 24volt (low voltage) drive motor, with the most common type of slats being solar PVC. They are hollow (like a double-glazing panel), coloured black underneath a clear top layer, and have a vacuum which heats up. They also have an air gap to prevent heat loss through the cover during the night.