Official Rules of Racquetball
4.3 - Fault Serve in Doubles
(a) The server's partner is not in the service
box with both feet on the floor and back to (but not necessarily
against) the side wall from the time the server begins the service
motion until the ball passes the short line.
(b) A served ball that hits the doubles partner while in the doubles box results in a fault serve.
(c) In one serve play, if a serve hits the
non-serving partner while standing in the box, the server will be
allowed one more opportunity to hit a legal serve. Hitting the
non-serving partner twice results in an out.
(d) In one serve play, consecutive faults –
such as (i) a screen serve followed by hitting the non-serving partner
or (ii) hitting the non-serving partner followed by serving while the
receiver is not ready -- results in an out.