  Let $L$ be a set of $n$ lines in $\reals^d$, for $d\ge 3$. A {\em joint} of
$L$ is a point incident to at least $d$ lines of $L$, not all in a common
hyperplane. Using a very simple algebraic proof technique, we show that the
maximum possible number of joints of $L$ is $\Theta(n^{d/(d-1)})$. For $d=3$,
this is a considerable simplification of the orignal algebraic proof of Guth
and Katz~\cite{GK}, and of the follow-up simpler proof of Elekes et al.
\cite{EKS}.
