How does your kata start? If you answered turn left and face your attacker, you win the booby prize. The lesson is close quarters, self-defense. Most kata start with your eyes closed, legs are straight, heels touching, hands held low and in front of you. In other words, you start from a position of vulnerability. As you open your eyes, it's like the curtains rising to a scene of your own mugging. Your assailant is in your face, maybe applying a front choke. What do you do?
In many kata, the first move is to drop your center of gravity and perform a juji uke. Juji uke (cross block), in this scenario, looks like you are crossing your wrists about face height (hands formed as fists) and bringing your arms down slowly to the sides. If instead of "blocking" you are grasping one or two digits of your attacker's hands placed around your neck, you can make use of the advantage of leverage, peel the attackers hands away and release the choke. Move your hands smartly, and you disable the attacker's hands. This is juji uke as small joint manipulation.
The rest of many kata offer similar scenarios united by a concept of close proximity. I don't for a minute believe any (okay, maybe some) of the bunkai offered by gurus that involve intercepting/catching a strike from the middle or long distance and then applying joint manipulations or throws. It's too hard. Complex motor skills against an ambush attack? Please. Test this out. Have a partner attack you with a barrage of strikes. More than likely, you'll flinch, cover-up, then clinch. The bunkai lessons can be applied once the grabbing starts. If there's no grabbing, run away while you have the chance.
Food for thought. Zenkutsu dachi gedan barai is a lousy block, which is how I learned it many years ago. In the "kata is in your face" paradigm, gedan barai is a great cross grab, wrist release technique: with your free arm smash down on your attacker's offending arm while simultaneously twisting and withdrawing your entrapped wrist (hikite). Of course, gedan barai might be used to block. . . knees for example. Is instruction required for something so instinctual? No. In the case of the wrist release application, the lowering of the center of gravity (zenkutsu dachi), the forearm smash (gedan barai), and the withdrawal of the entrapped wrist (hikite) combine yielding elegant bunkai.