Included below is a fun and interactive image that includes the names of things on the mainsail of a sailboat.
Take a look at the image and test yourself and your knowledge of the mainsail. Do you belive you can get 100% of the names correct? Click on a letter to expose the proper name and click again if you wish to hide it again. Have fun with it, and then share it with all of your sailing wannabe friends.
If you like this kind of teaching, you should take the NauticEd Skipper Course. That, and several other courses, are available to you with one click.