This is the most common meaning of "POS A4."

Purpose:

To display A4-sized graphics for advertising, information, or promotions in stores. 

Features:

• Size: Designed to hold standard A4 graphics (297 x 210mm). 

• Portability: Freestanding, with plastic feet or a metal base for stability. 

• Orientation: Can be used in both portrait and landscape formats. 

• Protection: Clear lenses protect the graphics from dust and grime. 

• Design: Features a simple, durable, and sometimes brightly colored frame to draw attention.