The homegrown dance festival Built on Stilts turns 18 this year with performances from Thursday to Sunday, August 7-10, and Wednesday to Saturday, August 16-19, at Union Chapel in Oak Bluffs. Each evening, the festival opens with a drum circle at 7:30 pm, which anyone can join, while dancers warm up. Self-choreographed dance pieces by local, national, and international performers follow at 8 pm. The lineup is different for each show. Admission is free, though donations are recommended. Visit builtonstilts.org for a detailed performance schedule.