If you are interested in a free Lean Six Sigma certification (the "White Belt") head on over to www.sixsigmasociety.org/ ... A poka-yoke is a product feature that prevents a mistake or defect from occurring (aka "mistake-proofing" device). They are popular tools used on Lean Six Sigma process improvement projects. There are three different categories of "poka-yoke" -- (1) the contact method, (2) the fixed value method, and (3) the motion-step method.