To begin making your PICA measuring instrument you will need 6 items:
1. Masking Tape
2. A Ruler
3. A Straight Edge (one which has either inches or centimeters)
4. A utility knife (not pictured)
5. A .3 mm Pilot Rollerball fine point ball pen
6. A fine point sharpie marker.
Step 1: Taping Your Ruler
Take a strip of masking tape, the length of the ruler, and place it so that it divides your ruler's measurements in half (covering one half). You can choose to cover either the inches or centimeters, this is up to you. I chose to cover up the centimeter side because I am used to working in standard measuring rather than metric. Using your utility knife, cut away the remaining masking tape from the edge of the ruler so that you have a clean edge and that your ruler rests completely flat against a table top.
Step 2: Making Your Reference Marks
1 inch is equal to 6 PICAs so therefore in order to establish reference points for your calculations you should find a suitable number of inches which you are comfortable working with. For me, 5 inches seemed to offer enough space for me to cover ground without having to reset and restart from a new reference point. Since 5x6 = 30 then I know that by making at mark at the 5, 10, and 15 inch marks, I've set my 30, 60, and 90 PICA marks.
Step 3: Recording Your PICA Points
So if 6 PICAs equals 1 inch, then what does 1 PICA equal? 1 PICA = 1/6th of an inch. However there are no 6th's degree of measurements on a ruler and that translation of measurement is also present within the metric system. Since the standard unit of measurement (inches) is broken down into 32nds (most common) or 64ths (if your ruler is one of more precise measurements) it presents a problem within the ability to become as finite as possible when making this ruler. The closest standard measurement to 1/6th of an inch is 3/16ths. Ideally we would want 3.333/16ths, but that isn't available to us. However, what is available are the measurements of tools which we have at our disposal, tools which have been majorly gauged using the metric system rather than the standard. The Pilot Rollerball fine point pen series comes in an wide variety of thicknesses, all of which go by the metric system of measurements. Using a .3mm point, and working backward from your reference points (inch 5 - 0), measure 3/16ths of an inch and then mark it, then measure down another 3/16th and mark. Continue to do so until you have reached 0. Repeat this step from each of your reference points, working in sections. Now take a sharpie fine point marker and trace over each rollerball pen mark you have made. What you should see is that the sharpie bleeds out the slightest bit over each of the marks you have made with the pen. This bleeding fills in the space needed to make up for that which the pen's measurements couldn't. The concept behind this is that if you make sure to use the smallest amount of material to cover a space, then you can build layers up within those smaller materials to better hone a more accurate measurement.