Hashem tells Moshe Rabbeinu, “I spoke to you from above the Kapores (the covering of the Aron).” Chazal learn from here that ten tefachim, which is the height of the k’ruvim which stood on top of the Kapores, is considered a separate domain. This is relevant to several halachos, particularly Hilchos Shabbos. The top of an object that is ten tefachim high in the public domain is considered a private domain, and therefore one is forbidden from transferring an object from the floor to the top of it.

Rabbi Aharon Dovid Singer
Rosh Kollel, NMB Kollel