Forgive me if there is already a thread with this heading. Sometimes I wonder about the things I do. Yesterday, I was pinning the tenons on a bread board end. I carefully drilled the holes, not too deep as these were to be blind pins. I had clamped everything together before drilling to get a nice tight fit. To my amazement, when i unclamped the bread board end with the pins installed, it came right off!

You guessed it, I drilled on the wrong side of the joint. I felt so foolish. Easily corrected and it won't be noticeable since it is on the bottom.