Quark with a neck brace
A neck brace was a medical restraint used to keep the neck motionless to allow proper healing of injuries.
In 2369, after Kira Nerys threw Quark over his bar, injuries he sustained from that incident required him to wear a neck brace. (DS9: "Dramatis Personae")
After T'Pol hit Commander Trip Tucker in the writers' second draft script of ENT: "Breaking the Ice", Doctor Phlox remarked that, if T'Pol had intended the assault, Trip would likely be wearing a "neck collar" rather than requiring simply an anti-inflammatory gel to be applied to a bruise on his cheek.