Roof knocking practice, in the sense of warning the inhabitants, was practiced since 2006. However, the non-explosive missile is reported only now, and [6] from the Roof-knocking article is no other than Gaza War Full of Traps and Trickery. I still don't see evidence this kind of missile was used before. If I am right, and this is newly-designed weapon, a means to spare lives - it is highly valuable encyclopedic data. Wanna another try?