The foreskin is the skin covering the glans of penis.

Frenulum

"On the underside of the glans, the foreskin's point of attachment is advanced toward the meatus (urethral opening) and forms a bandlike ligament called the frenulum. It is identical to the frenulum that secures the tongue to the floor of the mouth. The foreskin's frenulum holds it in place over the glans, and, in conjunction with the smooth muscle fibres, helps return the retracted foreskin to its usual forward position over the glans." ("Where Is My Foreskin? The Case Against Circumcision," by Paul M. Fleiss, MD, Mothering, Winter 1997)

"They told me there would be no pain ... a tremendous flash of blinding white pain surged through my entire body ... I thought I had been electrocuted and was dead ... The pain was the worse I have ever experienced ... I cannot imagine any pain possibly being worse." (From a letter to Rosemary Romberg, author of Circumcision: The Painful Dilemma, from a man in Florida, circumcised at age 25 under local anesthesia, describing what he felt when the doctor cut his frenulum.)

Foreskin Intact But No Apparent Frenulum

Why do some non-circumcised men have no apparent frenulum?

Because they were born without one?

Because someone broke their frenulums with a probe or by forcing their foreskins back when they were babies?

Because they accidently or deliberately broke their own frenulums in adolescence?

Because they cut their frenulums or had their frenulums cut when they were adults?

Is the percentage of males without apparent frenulums in the U.S. (where many non-circumcised males have their foreskins forced back in infancy or early childhood) higher than in countries where the first person to retract a male's foreskin is usually the male himself?

Mucocutaneous Junction

"Recently identified specialized erogenous tissue named the ridged band encircles the foreskin at its mucocutaneous junction (where the foreskin's inside and outside folds meet)." (Answers To Your Questions About Your Young Son's Intact Penis -- NOCIRC Information Series pamphlet #4)

Preputial Raphe

raphe n. a line, ridge, or crease in a tissue or organ, especially the line marking the junction of two embryologically distinct parts that have fused to form a straight structure in the adult. For example, the raphe of the tongue is the furrow that passes down the center of the dorsal surface of the tongue. The Bantam Medical Dictionary

Referrence:Foreskin(Chinese Version)