When can a black 3 be melded in canasta?

In the card game canasta, black 3s are generally not melded during standard play. However, there is one specific exception: a player may meld three or four black 3s only when they are attempting to "go out" (empty their hand).

When melding black 3s for this purpose, the following rules apply:
* Wild cards may not be included in a meld of black 3s.
* A player cannot go out if they hold only two black 3s and no other cards.
* If a player holds only one black 3, they may go out by discarding it rather than melding it.

Discarding a black 3 during normal play serves a strategic purpose, as it prevents the next player from taking the discard pile.1