knocking on the roof
n.— «The IDF has made frequent use of what is known as “knocking on the roof”: Militants are warned by phone when a residential building used to store arms will be bombed, and told to vacate the premised together with their neighbors. The weapons caches are hit only after the residents leave.» —“ Barak asks cabinet to approve emergency call-up of 2,510 reservists” by Amos Harel Haaretz (Tel Aviv, Israel) Jan. 1, 2009. (source: Double-Tongued Dictionary)