Often shouted in a public place (party, bus, etc) when couples are together. People who do not have significant others will shout this to keep themselves occupied. The couples must then raise their hands to show that they were not doing anything other than cuddling. It doesn't work. Trust me.
*Mo and Flo are at a party, hugging*
Joe: Yo, Mo and Flo! Hand check!
*Mo stops fingering Flo. Both raise hands into air*
Mo: See? We weren't doin' nothing!