If you read this blog — or any sexual health website, really — you’ll probably see dental dams getting a lot of props. A dental dam (not to be confused with a female condom) is a square piece of latex that can cover the vaginal opening or the anus. Anyone wishing to avoid the oral transmission of STDs like herpes, gonorrhea, HPV, syphilis, chlamydia, and intestinal parasites, dental-dam advocates say, should use a latex barrier. Most people, however, have probably never even seen a dental dam, and they are not widely used. Perhaps their unpopularity is related to myths about oral sex being safe sex (it’s not!); perhaps it’s due to dental dams being expensive or difficult to find.