Hamas is housing rockets in hardened silos

IDF found Qassam rockets in hardened silos built into the ground. These are similar to the silos used by Hezbollah for launching rockets at Israel. Either they are imitating them, or more likely, the same experts who built the Hezbollah silos are building the Hamas ones or guiding them:

 

Pictures released by the IDF Spokesperson's Office showed two underground
Kassam rocket silos, a meter in diameter and two meters deep. The launchers,
the army said, were big enough to hold a Kassam or Grad-model Katyusha
rocket that could be launched by remote control. 

 

Such silos are extremely difficult to detect from the air and are difficult to destroy, accounting for the ability of Hezbollah to fire rockets at Israel throughout the Second Lebanon War. The IDF believes that there are additional silos of this type throughout the Gaza Strip. The silos were discovered by the Golani Brigade's elite Egoz Unit during operations in Gaza. 

About 20 Qassam rockets and mortar shells hit the western Negev on Thursday, February 7, mostly near Sderot according to Israel TV Channel 1 news. Jerusalem post notes that one of the rockets hit a garage adjacent to a house in Sderot, causing a fire and sending three people into shock.