I believe you are asking about a shirt "placket. The placket refers to the double layers of fabric that hold the buttons and buttonholes of a shirt.
The word placard (noun meaning a sign, a notice, an advertisement) has no direct antonym; the closest would be 'without placard' or 'placard-less'.
The placard on the wall displayed the museum's latest exhibition information.
the placard have been posted everywhere.
placard means a poster for public display. Example: there was no placard outside.
Le placard (masc.) means the cupboard in English.
The DOT hazard classification system can be used to identify acute hazards.
dans mon placard means 'in my cupboard' in English.
It is a DOT hazardous materials placard indicating compressed oxygen.
You should place or install a placard along your truck, on the sides, or the front.
explosives
The cast of Mon placard - 1998 includes: Barbara Tissier
The laws and the rules governing disabled parking placard vary from state to state. However, all states require either a prescription from a doctor or a form from a doctor in order to obtain a placard. In addition, the placard is only to be used when the person that it is prescribed for is in the vehicle.