This weir is designed to use with pool and spa skimmer. Weirs allow water to flow into the skimmer, but close down when the pump shuts off preventing the back-flow of debris from returning to the pool. The string release style works by simply positioning the weir into place and pulling out the string at each side. The rod springs and locks into place. Skimmer weir measures 6-inch length by 5-1/4 inch width.