The Gemara on today’s daf continues the discussion of what rights are included in a standard sale agreement of a house or a piece of land. The Mishna teaches that someone who sells a house does not include the bor (pit) or dut (cistern), even if he included the terms umka ve-ruma – to the depths and heights – in the contract. These structures are considered to be separate from the house, and are, therefore, not included in its sale.
The Gemara appears to assume that both a bor and a dut are underground structures, and Ravina asks what the difference is between them. The Rashbam explains the question as asking why we should distinguish between them given that they are both underground structures whose purpose is to store water or other items.
In response, Rava Tosfa’a quotes a baraita that explains that a bor is simply dug in the ground while a dut is dug and then supported by construction. Most of the rishonim interpret Rava Tosfa’a’s statement as agreeing that they are largely the same, just the bor is in solid ground while the dut is in softer ground that needs additional construction to ensure that it does not collapse.
The Rambam, however, suggests in his Commentary to the Mishna, that the dut is a building that is constructed above ground. This appears to contradict the flow of the Gemara which is discussing structures below the house, and not free-standing buildings that are separate from the house. One approach is to suggest that the dut is built on the roof of the house – water storage on the roof was not uncommon in ancient Israel – and that the discussion is whether the seller included storage areas either below (the bor) or above (the dut) the house in his sale.