"Roof knocking" is a term I've learnt recently.
It refers to an initial low-yield blast on or above the roof of a building targeted for a subsequent attack.
It also explains why there are so many instances of cameras trained on buildings as they are struck presently in Gaza.
The idea is to give occupants an advanced warning and a few minutes to evacuate.
Contrast with the highly indiscriminate use of rockets by Hamas, though this also speaks to IDF's precision and ability to specifically target sites, and even portions of a structure to hit in order to level it.
There's also the Iron Dome system and its ~90% effectiveness in disabling incoming rocket fire, though at ~$100k+ per interceptor and ~3--5k incoming targets, that's up to about a half-billion dollars spent over the course of the past few days. Likely appreciated by those protected.
I'm not sure specifically what missiles Hamas is presently using, but Katyusha and Qassam missiles run about $800--$1,000 each based on what I'm finding.
One might describe this level of care for the wellbeing of your targets as unprecedented.
I am a resident of Israel. AMA.