Flat side to the needle bar will not always work but if you go from one machine to another it is a place to start most of the time. If you get into somthing really old or odd you might find a round needle or some other crazy thing and then the rule is: the needle curf goes toward the bobbin. No it is not a senior moment it is just something a lot of people don't generally know. Sewing machine needles are very confusing. I was given a couple machines because the needles were in backwards. People give up very easily some times. I have gotten machines that were caked with lint. I've seen 301's with the little thingy roaming free and so on. This forum is a great resource. Read. Read. Read. Look up in the upper section and search then read and search some more. Some of the longer threads have more info. Tammi has good info on her blog. Rain Noe has good info. Muv has a great blog. Dig around on line. Info is out there. Those people have left. I am taking care of elderly parents so I do not have a lot of time. There are some knowledgeable people on here still but information is likely already on here for the digging.