For example, copying the alphabet. Sometimes there is a glitch in the connection between your eyes and your hands that affects this skill. Children with poor handwriting often do poor on standardized tests of visual-motor skills. Children who have an auditory difficulty find it frustrating or impossible to take dictated notes or spell a word when sounding it out. Visual perceptual skills are required to accurately perceive letters and words.
Visual memory is required for spelling and for remembering how to form letters.
As an aside, visual-spatial skills have also been connected with mathematic abilities. Many parents tell me that when their child is really concentrating, their handwriting is much better. For children with TS, motor and vocal tics and obsessions and compulsions interfere with attention.