(quote from reference given)
The skin system of the penis
The intact penis is covered by one single continuous skin sheath or skin system. The skin sheath is partly folded at different times. This folded part of the skin system is called the foreskin or prepuce.

The fold of skin is often mistaken as a single layer, or a flap of skin. This is wrong. Instead, it is a free, two-layer fold that forms when the skin coming down the penis from the shaft folds underneath itself somewhere near the tip of the penis then travels back to an attachment point behind the glans (see figures 6 and 4). The two sides of the fold do not adhere to each other even though they lie flat against each other appearing to form a single flap of skin.