  The concept of jointness for guessing principles, specifically
$\diamondsuit_\kappa$ and various Laver diamonds, is introduced. A family of
guessing sequences is joint if the elements of any given sequence of targets
may be simultaneously guessed by the members of the family. While equivalent in
the case of $\diamondsuit_\kappa$, joint Laver diamonds are nontrivial new
objects. We give equiconsistency results for most of the large cardinals under
consideration and prove sharp separations between joint Laver diamonds of
different lengths in the case of $\theta$-supercompact cardinals.
