what is meant by street communication tool in the below sentence about an exhibition? thanks 4 help
Objects such as a bin lid used as a street communication tool in nationalist areas, a bullet-proof clipboard used by the security forces, as well as a matchbox with a well-known unionist slogan ‘Ulster says No’ printed on its cover are examples of the range of diverse objects on loan for this exhibition.

Question

Answer

It means they used the trash can bin lids to communicate with each other.

"In the Troubles, women would bang lids on the street to warn neighbors of British military raids. This would have a “viral” effect; the noise would spread down the street as neighboring women joined the chorus."

source: http://www.papermonument.com/web-only/see-something-say-something-11/