Alvin - Ames Lettering Cuide - Inch and Metric - The Ames Lettering Guide by Alvin is a uniquely designed instrument combining a rotating disk with an indexed rim for adjusting letter height or establishing cross-hatch marks. The Ames Lettering Guide has inch and metric line spacing. Size: 3-7?8 inch length x 2-3?8 inch height. Alvin is one of the primary sources for drafting supplies and drawing equipment in the country. Creative Coldsnow is a pround retailer of Alvin graphic arts, drafting and fine arts products.