I should imagine I shall now be killed and buried for this, but cart bait is basically the insides of an edible crab, entrails, brown and white meat juices etc that is pressed by hand into squares or sausages and frozen to make it "handle-able". It has to be fresh crab, from a fishmonger, and you get rights or very finemesh boilie wrap and place the bait into it tied off at both ends at the baits desired length. You then pass the hooklink snood through it with a carp stringer needle and freeze it bait, hook and all. It needs to be kept frozen until it hits the sea so transport in a Thermos is essential. It stinks as well. Take it to the shore in the flask, attach the snood to the rig and cast it out. It will defrost and the tights will keep the whole mess together but it washes out will need regular replacement. Other minced stuff can be added, mackerel, herring, sandeel, worms shellfish take your pick as large complete edibiles are not exactly common. Some people love it, others struggle, but some really guard its secret closely. The faster you can freeze it, the better so I put a large metal tray in the freezer beforehand so when the completed cart is placed on it, it freezes quickly.