(CNET) — Despite Facebook’s policies that make certain allowances for nudity on the social network, some artists say the rules prevent them from sharing their work online.

On Sunday, artist and photographer Spencer Tunick created a nude installation outside of Facebook and Instagram’s New York office with help from the National Coalition Against Censorship (NCAC). Dozens shed their clothes, lay in the street and used images of male nipples — which are acceptable on Facebook — to cover people’s nipples and genitalia.

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