Responsa for Bava Batra 104:12

Q. B bought property from a Gentile which bordered on A's property. Before paying for it, B, to acquire possession, did some digging in the Gentile's yard in the presence of witnesses. After B did so, but before he had paid the money to the Gentile, A constructed apertures for windows in his wall facing the property. Did A acquire rights to window lights?
A. In city property digging is not considered a valid act of possession. Likewise A did not acquire any rights to window lights since a Gentile does not renounce his rights to his property before he receives the money, and the Gentile's property was, therefore, not (res nullis) ownerless. However, before paying money to the Gentile, let B perform a valid act of possession (such as locking a door, fixing or breaking part of the fence, etc.); otherwise A will acquire rights to window lights during the interval between the paying of the money and B's taking formal possession, since during such interval the Gentile's property will be res nullis.
SOURCES: Cr. 63–64; Pr. 28–29; L. 338; Mord. ibid.

Q. Does a widow who is not admitted to oaths, lose her ketubah since she cannot take the required oath?
There is no answer to this query. The three questions bear the signatures of: Joseph b. Moses, Nathan b. Jacob, and Isaac b. Solomon.
SOURCES: Am II, 69–70.

Q. A widow seized notes of indebtedness and bonds of Gentiles, that were made out both in her name and in the name of her husband. Does this act constitute seizure of the debts?
A. The widow has to produce evidence to the effect that the money represented by the notes and the bonds was actually her money. Furthermore, possession of notes and bonds, does not imply the right to the money and property described therein. Thus seizure of the notes and the bonds does not constitute seizure of the debts.
SOURCES: P. 282; Mord. B.B. 562; Agudah B.B. 123. Cf. Maharil, Responsa 75.