Setts of 8, 10, and 12, and their metric equivalents, are the most common setts used on the rigid-heddle loom. See in an instant the spacing of any given yarn in the actual sett.
Now available in maple (light) and adler (dark) wood to offer contrast for dark and light yarns. Measures approximately 5” x 1”. A short 3” ruler etched on the side gives you a flat edge to check your picks per inch on and off the loom.
To take a deep dive into the sett checker and how to use it, check out this blog post.