While all capital letters stay between the cap height and baseline, lowercase letters descend below the baseline and extend above the x-height. To keep everything readable and harmonious, you can use the same guides for capital letters, and simply add a descender guideline below.

Four guidelines are needed for each row of lowercase letters. The tall stems touch the top guideline, which is generally the cap height of the capital letters. The lower stems reach the bottom guideline, which is usually the same distance from the baseline as the x-height is from the cap height.

Effective letter proportions for ascenders and descenders extend to guidelines

Letters do not extend to guidelines can appear out of place with the rest of the type.

When parts of individual letters do not connect clearly with each other, they can be difficult to read or recognize. This is described as the letters having "weak joints" and can cause the reader to stumble on a letter while reading. A "b" or "d" with weak joints could be mistaken for an "l" and "o" that are too close together. The image below is an example of lowercase letters with weak joints.