Using the Shrink Ruler is simple! Follow these steps:
 
Measure the final dimensions of your piece with a standard ruler.
Locate this measurement on the Shrink Ruler, using the scale that matches your clay's shrinkage rate. (your clay supplier will normally provide shrinkage % on the packaging or on their website)
Shape or mark your wet clay according to the Shrink Ruler's measurement.
After firing, your piece will shrink to the intended size.