These precision rulers have patented marking holes at each measurement where you can insert a thin pencil, pen or stylus and mark your measurement with accuracy.

They come in a variety of sizes to suit various book and box making applications:

3" pocket sized. $11.95
12" marking. $23.95
12" centering. $29.95
18" marking. $31.95
3" T rule. $15.95
12" T rule. $36.95
18" T rule. $46.95