One of the elements that separate how we at Movement Martial Arts approach all Martial Art is how small we look at it. Martial Art is just a collection of movements and all movements matter… especially hand movements.
Entire categories of Martial Art are defined by whether hands are opened or closed. But every Martial Art, including the grappling arts, have both open and close handed techniques. In grappling (submission or otherwise), offense is usually characterized by closing the space while defense is usually characterized by making space. In general, hand movements are no exception to this rule.
While the hand is capable of many degrees of articulation, let’s examine opening (extension mostly) and closing (mostly flexion) the hand. The very act of closing the hand moves the fingers closer to the body closing space while opening the hand moves the fingers further away from the body making space. It’s no coincidence that these actions of the hand correlate the offensive and defensive movements.
If opening the hand makes space, you can utilize this movement defensively in terms of a block. If closing the hand closes space, you can utilize this movement offensively in terms of a grip. While there are exceptions to this concept in grappling, try opening your hands in defense and closing your hands in offense. I think you’ll find your offense and defense more effective.