In creating the test, special antibodies that detect Coronavirus pieces (antigens) are adhered to the strip. They are placed in a horizontal band, and they are part of what helps to form the visual bands we see. Another antibody is also added that are designed to attach to the same antigens, but on the opposite side. These are placed onto the strip, but not adhered. As the sample flows up the strip, it will run into these free antibodies, and if there is a virus antigen in the sample, these antibodies will adhere to it, and continue to flow upward with the sample. These antibodies also have a marker on them that activate once they interact with one of the adhered antibodies. The image on the right helps to visualize what the positive test band looks like up close. For a better understanding of how the process works in motion, check out the video below.