Abstract: A ball and socket coupling in which the ball is positively retained within the socket by means of a cap, removably secured to the socket for closing the open end of the latter and having a hole through which the ball stem extends. The cap hole allows pivotal movement of the ball relative to the socket. The socket and the cap have inter-engaging interrupted threads for securing and releasing the cap by a simple one-quarter turn of the same. A lever is pivoted to the cap and engages between ears on the socket in the secured position of the cap to provide a safety lock. The resulting coupling is much stronger than conventional ball and socket couplings, because the cap forms an abutment face all around the ball.