The crab ride is a top riding situation in wrestling where you are sitting behind your opponent while he's in a sit-out. Your legs are stretched forward to get control of your opponents hips and legs. It's very important to use your feet to pull your opponents calves outwards while you use your knees to pinch his hips. Your hands should always remain on the inside of the arms fighting for different handles (Half Nelson, Claw, Two-On-One, etc).
This ride can be used to great effect when trying to throw legs in. Although the Crab Ride is one of the more favored positions of a leg-rider, it tends to be the most unstable. So, if you are defending against a leg rider and he happens to get legs in, it is best to force them to a crab ride so you can manage the situation better and escape easier.
Both you and your opponent will be in a sit-out position (sitting on your butt, legs stretched in front of you). You will hook your feet under his legs in front of his knees, gripping onto the sides of his shins, controlling the bottom portion of his legs. Your knees will pinch the hips in an effort to control his hips better. Try to keep your hands and arms underneath his arms at all times. Try to keep his hips sitting between your legs at all times.
Defensively you want to grab the soles of both feet as quickly as possible and pull his feet up to your hip. This will make it very uncomfortable for your opponent. Usually for someone to work with a crab ride their hands need to be under your arms, pulling your chest back away from your legs. If you’re holding onto their feet it connects the pulling of your shoulder to his feet. So when he pulls your shoulders it pulls his feet, making it very awkward for your opponent. This then gives you a few things you can look for.