Dave Grohl – one showing how to make a beer bong, the other how to smuggle hash into a gig – are up for auction. The Foo Fighters frontman created the two pieces for a charity auction in connection with the Sea.Hear.Now Festival in Asbury Park, New Jersey, which the band headlined this year. The first diagram shows how to construct a beer bong using a funnel, a clear tube and metal ties, and Grohl explained that he has been making the diagram for years to give to people backstage before concerts.