The grappling techniques of karate are classified as tuidi-waza (seizing hand techniques). This primarily refers to joint locks and grabbing/tearing techniques, but could technically include some types of chokes, throws and takedowns. We practice these in kata, in application drills, and in flow drills, but most people don’t work them in a randori (free grappling) scenario. Admittedly, free grappling with a similarly trained opponent isn’t really the proper context for tuidi, and is very difficult to do, in comparison to applying tuidi to an untrained opponent. Also, some of the techniques really can’t be done to completion, for safety, because they are meant to be applied very quickly. That said, it is still possible to use it as a very effective tool for refining your understanding of tuidi, and putting it to the test against a resisting opponent.
In the video, above, you can see some examples of what I call tuidi-focused randori (free grappling). In this type of randori, both partners are intended to remain at clinching/grappling range the entire time, with grappling techniques being the primary fighting methods used, although the occasional strike is allowed. You can also set different goals, depending on what you are working on. You can have them focus entirely on standing techniques, or you can focus on throwing the opponent to the ground, or you can focus on groundwork. Regardless of the scenario, it should be totally free-form within that scenario. While the video above shows tuidi-focused randori with very little striking, any viable technique (or simulated technique) can be included, whether it is a strike, lock, throw, or choke. Ideally, you want to incorporate technique sequences from your kata wherever they fit. This helps you get used to striking while applying tuidi techniques, but it also keeps you honest, because if you leave yourself in a position where your partner can hit you, they will.
While it doesn’t fit into jiyu kumite (free sparring) the way most dojo typically practice it, tuidi can also be incorporated into MMA-style sparring, so long as all participants know that it is an option. You can see an example of tuidi applied in MMA in the video, above, where UFC Light Heavyweight Champion, Jon Jones, uses an elbow wrench that can be found in Naihanchi Sandan. Since MMA-style sparring is not typically grappling-focused, the way randori is, you will not have as many opportunities to use tuidi techniques. Since you will also be facing someone who has trained in a striking art, it will be harder to trap their strikes than someone who is untrained. Even so, you can find ways to slip them in. This is a great way to pressure test your tuidi, since it is fairly difficult, and your opponent can resist and strike you, much as they would if it were a real self defense situation.