If you have a thurifer/censer, this is the incense holder.  I used to use a mortar and pestle to grind down the incense, then try to pour the heavy stone mortar towards the mouth of the boat...but that didn't turn out too well.  A coffee bean grinder where the top detaches as a small bowl, though, really worked fast and ground the incense down enough to smoke well.  It made it easy to transfer it into the boat, closely, and from there to the thurifer.