Before typewriters and other methods were developed (printing press), how did people hand-write important documents with such precision? For example, the Declaration of Independence. The lines seem to be perfectly level and aligned with uniform typography. How is that possible to do by hand?

by Alexanderr

Here is a photograph of the Declaration of Independence copy that I'm referencing. I'm wondering how people hand-wrote documents such as these with such precision.

WARitter

The answer by u/rimeroyal to this question goes into this process in some detail, with a focus on the Middle Ages.