Yelp I see this every so often with bar blades. Customer want me to sharpen their blades and I ask if they just want to put the blade on correctly and it still has a nice sharp edge.
And must not forget those chainsaws that comes into to shop that will not cut where the chain is on backwards. And I have install them backwards myself a few times but it is to use them as debarkers. I did one time forget to take off my dumby chain (one with no cutters) off and delivered the repaired saw back to the customer. Boy was he mad until I explained why I had the safety chain on the saw then we had a good at my expense. Glad to get back that chain though as they are hard to come by unless you make your own.
Reckon he would have got a lousy finish on his lawn. 
