Figure 3-4 Mistake-Proofing the Design of Health Care Processes - Figure 3.4. A typical pin-indexed medical air outlet The pins on the regulator fit into the holes at 12 and 5 o'clock. Each gas regulator has a 12 o'clock pin and one other pin.Return to Document Current as of May 2007 Internet Citation: Figure 3-4: Mistake-Proofing the Design of Health Care Processes -. May 2007. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/professionals/quality-patient-safety/patient-safety-resources/resources/mistakeproof/mistakefig3-4.html