Zip

A zip was a mechanism used to join two edges of clothing together. Human skin suits used by the Slitheen were fitted with zips on their foreheads. (TV: Aliens of London/World War Three) In reference to this, the Tenth Doctor asked Donna Noble if her fiance was "a bit overweight with a zip around his forehead." (TV: The Runaway Bride)

Raxacoricofallapatorian skin suits used by the Ninth Doctor and Jack Harkness had zips located on the neck, under the collar. (COMIC: Doctormania)