Personal Drafting Machine Easily clamped onto any drawing board up to 1-3/8" thick. Protractor arms are made of 1/2" steel tubing. Measures 24" long and is suitable for graphic artists and any other professional designers. Drafting head is mounted to the vertical runners and is precision made. Comes with inch rules. Model 91009 is an omnipotent drafting machine with new style. Simple operation and high accuracy.