Four interlocking resin plates that anchor a cantilever or offset umbrella once they are filled on site. Empty, the set weighs 22 lb and lifts by the recessed handles; filled with water it holds a 350-lb load against the arm of a hanging umbrella. Wide fill ports let a garden hose top up all four plates quickly, and rectangular connectors clamp them into one 41-in octagonal ring around the upright. The weather-resistant black surface resists staining and rinses clean, so the set can stay outside on a garden path, a courtyard, a porch or beside the pool through the season.