The boards are useful for puck transportation both in defence and offense.

Instead of dumping the puck, a slapshot via the boards is a very good way to get the puck out of the zone, and as a bonus you won't risk putting the puck over the glass when on PK.

When attacking, using the boards is a snekay and pretty safe way to get passes through to a player behind the net. Also (and this is pretty obvious), if it looks like you're going to get body checked, shoot or pass the puck along the boards to avoid a counter attack.