About this Mistakeproofing Website

Mistakeproofing is “the use of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred (ASQ 2019).” It’s called poka-yoke in Japanese.

Let’s not argue about spelling: “mistakeproofing” is also spelled “mistake-proofing” and “mistake proofing;” we’ve picked one and use it consistently. It is also known as error proofing or fail safing; these words too may also be spelled as a single word or with a hyphen.

The objective of mistakeproofing is to reduce the likelihood that errors will occur and, should they occur anyway, to prevent that they turn into defects.

Website Organization

To inspire people, promote conceptual understanding, and encourage the practice of mistakeproofing, this website presents more than XXX examples as of June 2019. We’ve categorized them in five different ways to help you find them.

  1. 6 Mistakeproofing Principles
  2. 40 Principles of the Theory of Inventive Problem Solving (TRIZ)
  3. CSI MasterFormat®
  4. OmniClass™
  5. OSHA Hazard Controls

Select the corresponding menu item to learn more about these categories and their rationale.

Please Contribute

Sends us your examples if you’d like us to share them on this site! Select the menu item CONTRIBUTE to provide specifics. We reserve the right to decide whether or not to post what you submit, and what text and images to post online. Though we want to avoid advertising to the extent possible, of course innovations and brand names have to be recognized. For any specific type of example, we have not even tried to list all possible manufacturers. Some products in the catalogue may also be taken off the market and that’s beyond our control.


This website was developed by Andrew Peña (in Spring 2019, while a UC Berkeley Master’s student in Engineering and Project Management) with layout input and numerous examples provided by Iris D. Tommelein. Iris D. Tommelein owes thanks to students, colleagues, and industry practitioners who over the course of many years have suggested examples of mistakeproofing, many of which are included in this online catalogue. Tommelein and Demirkesen’s (2018) study relating mistakeproofing to TRIZ was made possible by member contributions to the Project Production Systems Laboratory (P2SL) at UC Berkeley, and by CPWR (The Center for Construction Research and Training) through cooperative agreement number U60-OH009762 from the National Institute of Occupational Safety and Health (NIOSH). Maintenance of this site is made possible by member contributions to the Project Production Systems Laboratory (P2SL) at UC Berkeley. If you wish to support our Lab, select the menu item FUND to provide specifics. This website’s contents are solely the responsibility of the authors and do not necessarily represent the official views of members of P2SL, of CPWR, or NIOSH.