We went to Lowe's to get a sheet of plywood for the latest home project. The sheet needed to be cut down to the dimensions Lisa had worked out, and I read them and (I thought) marked them on the plywood. But after we got the sheet cut and Lisa started to look for some other things, she re-measured the cut sheet and found that I'd marked it wrong. So there was nothing for it but to get another sheet and get it cut with the correct dimensions. That's a $36 mistake. However, Lisa does say she'll be able to make some use of the mis-cut sheet, so it's not a total loss.