This construction is used when the width of the pool becomes tapers off towards the bottom. The roller system should, if possible, be positioned on the skimmer side so that, in the case of an outdoor pool, the coarse contamination is transported directly in front of the skimmer.
| Construction: | Roller system mounted directly below the surface of the water |
| Installation: | New or subsequent fitting |
| Maximum size: | 25 m x 50 m (larger sizes depending on pool shape) |
| Drive unit in separate motor pit: | Drive unit mounted on the shaft, or chain drive |
| Drive unit without motor pit: | Tubular motor (not always possible, dependent on pool width and depth) |
| Cover slats: | Standard slats 60 mm wide and 14 mm thick |
| Guidelines: | Installation approved only for private pools |