The KS0108 chip draws 8 vertical pixels at a time.
The T6963C chip draws 8 horizontal pixels at a time. Or if you set the FS pin on many modules it draws 6 horizontal pixels.

To draw characters from a font, you just set the correct bits in each scan line byte. A tall character obviously uses more scan lines.

Life is considerably easier if your font data is arranged by horizontal pixels. You still have to cope with overlapping scan bytes when you have variable width fonts.

The built-in 8x8 font or 7x5 font line up neatly with the 8 or 6 pixel byte.

David.