Question: I am looking for a rule on competitive co-ed blocking.  When is a male allowed to come from the back row to block, and when are they not permitted?

STEVE WEBSTER responds:

Co-ed rules can be found starting on page 108 of the 2013-15 DCR.  The rule you are looking for is 1.4:

1.4 When only one male player is in the front row at service, one male back-row player may be forward of the attack line for the purpose of blocking. The remaining back-row player must be behind the attack line until the ball has been contacted by the blocker(s) or has been hit in such a manner that no block is possible.

1.4 Commentary: If a back-row player is not participating in a block, there is no restriction on both back-row male players being in the attack zone.

1.4.1 The provisions of Rule 13.2.2 shall govern male back-row players when playing the ball in other than blocking actions.