As can be seen from the two tables above, components in the MCT are grouped into 17 categories according to their shape. First a global distinction was made between components containing mainly slanting strokes, such as 立, 乃, 毛, and 大, which were placed in the first half of the MCT, and those consisting mostly of horizontal and vertical strokes, like 惠, 半, 并, 口, 日, and 典, which were placed in the second half.
The first group (see Table 1), those with slanting strokes, was further split into 10 categories by looking in more detail at their shape and by grouping components sharing a certain feature. For each category the component that shows the typical feature most clearly was chosen as representative (“rep.” in the tables above) for that particular category and placed at its beginning.
For example, components that all have one or more strokes that bend to the right at the bottom, like 匕, 屯, 电, and 艮 were placed in category, 7, which consists of two subcategories. The first subcategory contains components with one ‘foot’ to the right, and the second contains components with two or more ‘feet’.
The second group (see Table 2), consisting of components with horizontal and vertical strokes, was split into six categories (see categories 11-16). Besides these there is a ‘rest’ group, forming category 17. Category 11 can be seen as intermediate between the two groups, containing diverging strokes and horizontal+vertical strokes.
Next: How to look up characters in the CCD.