Why is there a crease in my nail

Q. You wrote about weak, brittle fingernails with longitudinal ridges. I have strong nails with horizontal ridges. What causes this, and what can I do about. 28 May, What do vertical nail ridges mean? Lines running from the bottom of the nail to the tip are the most common form of ridges in fingernails. Nail ridges are raised lines in the nails of the fingers or toes that may run vertically along the nail or horizontally across the nail.