Frenulum is any small fold of tissue that has a role of securing a mobile part of the tissue. A frenulum also serves to restrict the movement of the tissue. There are many frenula on the human body located at various areas, such as brain, mouth, digestive tract and genitalia. Perhaps the most popular ones are the frenula located inside the mouth. Oral frenula include a frenulum under the tongue, the one inside the upper lip, the one inside the lower lip and one that connects the cheeks to the gum.

In practice, a frenulum is a thin tissue that can easily be pierced. This is why it’s not surprising that there are many frenulum piercings, particularly in the mouth. For example, a tongue web piercing is a piercing done on the frenulum under the tongue. It is also possible to pierce a frenulum of the upper lip to create a Smiley piercing. A corresponding piercing done on the frenulum of the lower lip is known as a Frowny piercing. A frenulum is also located on the penis: it is an elastic piece of tissue that connects foreskin to the glans of the penis. This should not be confused with the frenum piercing, which a piercing is done on the penis skin underneath the glans of the penis. Generally speaking, only uncircumcised men have frenulum of the penis but you don’t need to be uncircumcised to get a frenum piercing.