Width of Edging:
Size 10 thread, 1.5mm hook = 1/2”
Size 20 thread, 1.15mm hook = 3/8”
Size 30 thread, 1.00mm hook = 1/4”

This is the actual name of the pattern in the book. There are also knit and tatted edgings, so I assume they are named with the craft included for ease of reference.