Waiting at airports for people to arrive can be tedious. So Polish charity Itaka Center for Missing People and agency Isobar Poland came up with an idea: handing out free arrival signs at airports for people to write on. On the blank side, they write the name of the person they're waiting for; on the back are details of a missing person. The idea, as this case study explains, is that the person holding the sign has plenty of time to take in the missing person's face and details while they're hanging around in the arrival hall for their friend or relative. According to the charity, 17,000 people go missing in Poland every year. So far, the signs have been used at the country's two biggest airports in Warsaw and Krakow.