Of all the tools used in drafting, the one that has a huge potential for calligraphers is the Ames lettering guide with its small size and rotating disc will take the stress out of marking parallel lines on pages so much easier.
This tool will allow you to quickly produce evenly spaced guide lines for writing, (other uses are for architecture or engineering work). The holes in the tool allow for consistent spacing, with the rotating disc allowing you to vary the size of your letters body height (x-height).
Note: When used in combination with a t-square, ruler or other type straight edge this guide tool allows you to create precise lines with equal spacing without measuring the space with a ruler.
The Ames Lettering Guide has a clear plastic frame with a rotating disc with columns of holes in it. Where the vertical distances between the holes can be adjusted quickly to give the desired spacing for guide lines by rotating the disc to one of the settings indicated at the bottom of the disk.
Note: The numbers at the bottom of the disc indicates height of letters in thirty-seconds of an inch. Thus setting at the Number 4 setting, the lettering height would be 4/32” or 1/8”.
The center column of holes (evenly spaced holes) are used mainly to draw guide lines for numerals, fractions, and general lettering. The height of whole numbers and general lettering will be two units and the height of fractions will be four units. With the sides of the guide being used to draw vertical or inclined guide lines.
Note: If a project requires opaque paper or makes using a light box difficult, then using this tool can help you.
A. Two-Thirds Ratio – These holes are arranged so that lowercase letters are 2/3 the size of capitals
B. Equal-Spaced Ratio – Using these holes makes guideline layout easy.
C. Three-Fifths Ratio – These holes are arranged so that lowercase letters are 3/5 the size of capitals
D. Disc Number – Numbers 10 — 2 denote the height of letters in thirty-seconds of an inch. If 1/4″ high letters are needed (ie. rotate the disc so that the number 8 is at the frame index mark (8/32″ = 1/4″).
E. Frame Index Mark – This is the indicator that defines the character height with Disc Numbers
F. Metric System – Letter heights will be in mm
G. Slope Lines Guide – You can flip the 68-degree diagonal right side over to use as a guide for the “slope” of italic characters.
H. One Eighth Holes – These holes are 1/8 inch apart which makes it great for calligraphers.
Image from artofthecomicbook.com
Video on how to use an Ames lettering guide by jetpens