Changes

The double-layered design of the [[foreskin]] does indeed permit smooth penetration and a sliding action. The [[skin]] of the [[penis]], including the foreskin, becomes rougher during [[erection]]. This roughness is brought about by a mechanism similar to that which raises goosebumps. The extra frictional resistance brought about in this way reduces slippage of [[penile skin]] against [[Vagina| female tissues]]. The double-layering of the foreskin is designed to offset the frictional effect of erect [[penile skin]] and allow for easy vaginal penetration.