The ANAR Foundation is a Spanish organization which helps kids in risk. They Operate a unique phone number – 116 111 – where minors at risk can get aid and consultation.
Anar did a campaign advertizing the number, but were facing a problem where they did not want potential aggressors to see that a kid was even looking at the ad.
The solution was using Lenticular printing on street signs. According to Wikipedia, Lenticular printing is a technology in which Lenticular lenses (a technology that is also used for 3D displays) are used to produce printed images with an illusion of depth, or the ability to change or move as the image is viewed from different angles.
So Lenticular prints are unique in the way that they display different images to viewers at different angles. You may remember Lenticular images from when you were a kid and everybody had a magic ruler that changed shape back at school.
Anar created a poster that conveys a secret message to people at different heights, even if accompanied by a potential aggressor.
They calculated the average height of a 10 years old kid and planted a message only seen when looking at the poster from that height.
Adults would see this innocent poster
While kids would see this poster with an injured kid and the number
Here is a short movie explaining the project
Thanks for the heads up, Taeer.