Hopkinton Cub Scouts Pack 4, for boys and girls in Grades K-5, will host an event open to the public on Wednesday, Aug. 16, from 6-8 p.m. at the MetroWest YMCA Recreation Lodge (45 East Street). The event will include water bottle rocket launching, rock climbing and ice cream, and attendees can learn more about Cub Scouts. For more information, visit the Pack 4 Facebook page @pack4hop.