806. The Buyer's Right of Access

114:3 After one has sold the chometz, if he is concerned that it might be damaged by the buyer, he may set a boundary to protect it. (The Mishnah Brurah does not permit this - MB 448:12.) If the non-Jewish buyer wants to leave the key with the Jewish seller, he may. However, the Jew is not permitted to put a seal on the chometz.

114:4 If the Jew is unable to rent the whole room to the non-Jew because he will need to use it, he should erect a partition in front of the chometz and rent the non-Jew the space up to the partition; this must be written in the contract. (The partition must be ten handbreadths tall, which is about 35 inches - OC 440:2. Hanging a sheet doesn't work unless the bottom is tied down - MB 440:12.) He must also write that the buyer has right of passage to reach that place as he desires. Also, if this non-Jew chooses to sell the chometz to a different non-Jew during Pesach, or to a Jew on the day after Pesach, all of them enjoy the right of access to get to the chometz. Similarly, if one rented or sold the non-Jew a room that can only be accessed via the seller's property, he must write in the contract that the non-Jewish buyer and any subsequent buyers enjoy the right of access to get there.