Richard M Prescott Valley , AZ January 29, 2016 Control knob came off and would not snap back on the two pronged shaft I went to the Appliance Parts Pros website - did a search with what I thought was the Model Number of our Whirlpool Washing Machine. When I looked at the photos of knobs I choose one that looked right and ordered it. When it came it did not fit. So, I tried again. This time I spoke with the Parts Pro and she told me where to find the Model & Serial Number - way down on the back of the machine on a little square tag. She searched with those numbers and provided the correct part, which snapped easily and securely in place on the shaft. Repair done. Lessons learned: 1) find and use the Mod and Serial numbers - don't guess, 2) When I doubt speak to a pro who is knowledgeable and patient. 3 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes