This is my most successful version of a modified ball & socket joint to be used in the design of articulated figures. The built-in ball & socket components in tinkercad are okay, but I've found that they become too loose over time.
I wanted to design a joint that would allow for decent articulation and stay connected when posed and manipulated.
This design has a ball with two small tabs which line up with respective slots in the socket. If the ball is twisted after entering the socket, it should lock in place and allow for a reasonable range of motion.