Virtually all the designs and patterns on the card have some significance. Along the top (see above) are 95% saturation colour-bars in descending order of luminance—white, yellow, cyan, green, magenta, red, blue and black. There are triangles on each of the four sides of the card to check for correct overscanning of the picture. Standard greyscale and frequency response tests are found on the left and right respectively of the central picture. On the updated version known as Test Card J (including widescreen and HD versions), the X on the noughts-and-crosses board is an indicator for aligning the centre of the screen.