IN: https://www.handspeak.com/word/search/index.php?id=1112 This sign for IN is used for describing physical location. It would not be used in phrases like "in July" or "in my opinion." ON: http://www.lifeprint.com/asl101/pages-signs/o/on.htm Again, this describes a physical location. You wouldn't use it in phrases like "on Thursday" or "on a trip." AT: http://www.lifeprint.com/asl101/pages-signs/a/at.htm ASL does not correspond exactly to English. It has its own grammar rules. Asking for individual signs without any context won't help you much. This man makes excellent videos about ASL: https://m.youtube.com/watch?v=uPKOwziViaw Be careful, because there are a lot of inaccurate ASL videos on YouTube. I recommend learning either from Deaf people, or hearing people who have Deaf parents.