This is an under track system, on a pool with a rock edge feature, blue fabric, closed.  Copyright Ellis Pool Covers, 2003.

Ellis Pool Covers Inc. ◦  Sales, service, and local distributor of automatic swimming pool covers in Southeastern New England, (Massachusetts) USA ◦  14 Roberts Road Plymouth MA USA, 02360 ◦  (508) 746 1701 ◦  Fax (508) 746 1702