A small black line that forms vertically underneath your nail may be a splinter hemorrhage, while horizontal lines may be melanonychia. These may be harmless or a sign of a more serious health ...

A black line can also stretch horizontally across the nail (horizontal melanonychia), though this is rare. Depending on the ...

Picture interference, including horizontal black lines, may appear suddenly even if the TV worked fine before. Often, changing your Sony TV's settings makes horizontal black lines disappear.

A Reddit user shared a photo of their nail showing a “black line,” and was quickly advised by other users to see a doctor ...