In order to discreetly reach abused children, one aid organization designed a clever billboard that
only displays a hotline number for people shorter than 4’5″. The secret is a precisely serrated surface, a
Lenticular lens, that reflects light differently to those looking from above and below a specified height. Shorter people (children) see the following message on a street sign: “If somebody hurts you, phone us and we’ll help you,” along with a confidential number to call the Spanish organization, Aid to Children and Adolescents
.