You can watch a live action demo from one of my students in the video clip to the right. Although he moves across a room, this can be done backwards and forwards on the spot just as easily. You can also make the excerise harder or easier by changing the surface you work on.
The sidewinding action simulates the movement of a snake and allows us to develop a natural movement on the ground without the direct use of our hands and legs for leverage or traction. So why is this useful? Two main reasons: 1) Especially whilst executing BJJ / ground-based techniques, our arms and legs may well be busy; and 2) Throughout all the different aspects of martial arts, shoulder and hip rotation / twist is a vital movement. Sidewinding is also excellent for building core strength.
There are numerous ways to improve your game which don't involve actual work with a partner. This is particularly useful if you're unable to get to class, have a minor injury which prevents full participation or simply want to improve outside of lessons. Aside from revising technique details / running orders and visualisation, there are a number of physical drills that you can do as well. Quite a few of them, like this one, don't necessarily require a lot of space, which make them ideal if you travel a lot and wind up cooped inside a hotel room.
No, not drilling with an electric or pneumatic drill...
The art and skill of drilling is often an undervalued practice. Which would you rather? Know three moves and be able to use each with deadly precision and perfection or have a repertoire of three hundred moves which you can't recall or execute under pressure?
"I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times."
_Coming from Bruce Lee, it's a sobering thought. Now I'm not saying that you should only learn one move, or even three; I enjoy a lot of variety as much as the next person. However, I would caution the serious martial artist that if you want to be really good under pressure you have to drill and pressure test.