Bring your worn out, broken, or just plain painful flip-flops to the store any time until May 21. An international recycling company is collecting used flip-flops at all Old Navy clothing stores until May 21. The program started on Earth Day. The flip-flops will come out on the other end as ground covering for public playgrounds—those rubber-like surfaces that save teeth, knees and arms when children take a fall. Betsy King, the district manager for Old Navy in the St. Louis region, said that four playgrounds will be built and filled with the recycled flip-flops. King said there's no word yet on which communities those playgrounds will be built in.