Vertical window blinds are connected together at their lower end by a molded bead string. At a set distance there are hooks which connect to the blind weight. After time these hooks become very brittle and eventually break allowing that unsupported section of bead string to hang down in an unsightly loop.

This Thing will replace broken hooks but the old hook needs to be chipped away first - without damaging the string. I have found a pair of end snips very effective.