Arguably the most important aspect of grappling is to establish GRIP Control. Very similar to GRIPS is the concept of HOOKS. Hooks are used very similarly to grips in where you are catching, pulling, holding or suspending. This is exactly one of the definitions of a hook: Hook definition, a curved or angular piece of metal or other hard substance for catching, pulling, holding, or suspending something. A strong hook feels similar to an anchor gripping and controlling your limb. In order to be able to establish strong hooks, your toes must be alive, active and point upward so that your feet are creating a 90 degree angle (aka right angle). The more acute the angle the stronger your hook will be. If your toes are pointing outward (ballerina toes), your opponents limbs will slide off and you will have no control of your opponent for position. This is why, your hooks have to be strong at all times; just as strong as GRIPS. Here are a several positions which you must establish strong hooks: Top position on a turtled opponent (getting your hooks in); Butterfly Guard, RNC back-take; Lasso from Guard, Full Mount Top Position (spreading out your opponents legs) X-Guard Position, DeLaRiva.
Depending on the position of the opponent, a strong HOOK must be in motion. Thus, your toes are alive/active and your hook must be in motion. A stale non-active hook will be stuffed or passed by an aggressive guard passer as in butterfly guard. For example, the hook is more effective while in motion as your knee and hook are pulling on a standing opponent’s leg. Using this method, the process of control is distributed from the hook to the grip on the standing opponent’s leg. Keep in mind that you must either have grips established or appropriate foot position from the non-hooking leg which may be pushing off the opponent’s hip or off the opponent’s bicep on the opposite arm. The main point is that the HOOK must be active and consistently in motion countering the base/balance of the opponent.
Below is the Wikipedia definition of hooks as it relates to grappling and a very good video by Professor Emily Kwok on hooks when used with butterfly guard
Here is a video of two of my favorite back takes from butterfly guard which easily convert to sweeps and leglocks - https://youtu.be/i3o4bqWUyn4
Professor Frank Garcia