Spain's Anar (Aid to Children and Adolescents at Risk) Foundation currently uses an ad that shows different messages for adults and children - but at the same time. A lenticular top layer makes this possible and folks under 4'5" (usually kids) will see stuff taller folks won't see. The idea is that often the abuser might be with the child and would not stop if they saw the complete message. So indeed, "sometimes, child abuse is only visible to the child suffering it. "
Only kids will typically see this.