One thing I never like to admit!
I was installing a new intake on my 340 dart one day, and working at my parents auto repair business at the same time, I had everything ready to put the intake on, and laid one of those red cotton shop rags across the lifter area, to keep things from possibly ruining my nice clean prepared surfaces and thinking I would just lay the intake and carburetor on for a second to see what it looked like, how tall, etc....Well, you can tell where this is going? The shop got busy all of the sudden and a few hours later, getting back to "my" favorite project...I forgot about that rag! I spent lots more time getting the rag out of the oil pump drive and oil pump and oil filter!!!! What a mess!
Thanfully, my Brother's and Dad have forgot and never mention it anymore! That was about 20 years ago! And I ALWAYS check even the small things and never get in a hurry anymore, at least on My stuff!