Brazilian Jiu-Jitsu is an incredible mish-mash of information, and looking for help can often be like drinking from a fire hose: you often get more info than you want, and it can be really confusing. Methods like this (left, right, over, under) can be extremely useful in categorizing and simplifying your understanding of jiu-jitsu, and you can often use this type of study aid to help you figure out your own (often unexpected) solutions! As always, please let me know how these techniques are working for you. It is always gratifying and incredible to me to hear that one of these tutorials has helped you from across the Internet!