John loves to grab, kiss, suck or lick on and randomly touch Sherlock at random times sometimes it leads to sex sometimes it doesn't but it always leaves Sherlock feeling claimed and owned like John's marking his territory. For example, when Sherlock's sitting at an experiment John might come up behind him and suck on his neck as he slips his hands under Sherlock's shirt and pinches his nipples and then walks away to go to Tesco or something mundane like that.