Q: I found a knapsack with clothes in it. How am I supposed to publicize this?

A: In the times of the Beis Hamikdash, people would publicize the aveidah on the Festivals, when all the Jewish people would assemble in Yerushalayim. After the destruction of the Beis Hamikdash, the Sages instituted the procedure of publicizing in shuls and batei midrash. When this became impossible, they established that one must notify one’s friends and neighbors (B.M. 27b).

Nowadays, one should publicize in such a manner that the owner will most likely hear about or see it. This includes public places in the vicinity of the lost item: shuls, public bulletin boards, etc. For expensive items, you can publicize in a local paper and recoup the advertising cost from the owner (Hashavas Aveidah K’halacha 3:1).

You should identify the item in a general manner: knapsack with clothes, sweater, bicycle, laptop, etc., without divulging details of the item. The person who lost the item should provide details as simanim (C.M. 267:3-4).

The notice should remain posted long enough for the owner to see it; this would be at least a week or two. If the notice is removed after this time, there is no need to replace it.