The Pool Sentry M3000 Pool Water Leveler is used to maintain the water level of a pool, spa, or pond automatically and unattended. The Pool Sentry is easily assembled by snapping together two parts and threading in the valve box assembly. No tools are required for the simple installation. It includes a heavy plastic sealable pouch which you fill with rocks or pea gravel and use as a weight to hold the unit onto the deck. The bag is placed inside the cavity by removing the top cover. It is then attached to a garden hose and the water is turned on.