Piercing of the foreskin is done mainly for its decorative effect. It adds little to the pleasure of intercourse. Some men find it erotic in foreplay particularly if they have a sensitive foreskin!
Foreskin piercing has its origins as a means of ensuring chastity through the practice of Infibulation. A ring or similar device is used to hold the foreskin closed preventing the wearer from having intercourse and making erection somewhat painful! This practice has some attractions to aficionados of bondage and discipline scenes where such restraint can be very erotic.
Rings and circular barbells are very popular in foreskin piercings. A range of novelty jewellery including padlocks (working and non-working models) are available if required.