Q 1: Instead of publicizing an aveidah, can I simply hang the lost item on a nearby bulletin board or fence?

Q 2: If I find a lost item with a clear name and address, do I have to bring it to the owner? Is it acceptable to leave it in his property?

A1: When you find a lost item, you are responsible for it as a shomer (guardian), and cannot leave it in an unsecure manner.

Therefore, you cannot hang it on the bulletin board or fence unless you are sure that the owner will pass by shortly or that no one else will take the item from there. Otherwise, there is a chance that it might be stolen (C.M. 267:1; Hashavas Aveidah K’halacha 3:6-8).

A2: You are required to care for the aveida until it is returned to its owner. However, it suffices to notify him, and he should arrange to retrieve it from you.

You can also leave the item in his property if it is secure there, e.g. an enclosed yard or in the mail slot, or if he is expected to arrive shortly and will see it (Pischei Choshen, Aveidah 7:1-2[2]).