710. Making a Pit Deeper or Shallower

Shabbos 14:20

If a person removes a clod of dirt from the bottom of a pit that is nine handbreadths deep, thereby making it ten handbreadths deep (and therefore the dimensions of a private domain), he is not liable. This is so even though removing the dirt and creating the private domain happen at the same time because the pit was not ten handbreadths deep at the outset. Similarly, if a person throws a clod of dirt into a pit that is ten handbreadths deep, making it less than ten handbreadths deep (and therefore no longer a private domain), he is not liable because placing the dirt and nullifying the domain happen at the same time.

Shabbos 14:21

If a person throws a board and it lands on spikes sticking out of the ground in the public domain, he is not liable even if doing so results in the creation of a private domain, and even if some utensil is on the board. This is because the domain is created at the same time that the utensil comes to rest.