You can select a tower for example a spike factory and you can make it "feed" the shrapnel, the the spikes (or whatever the tower makes) made will go into the top and all of the projectiles will be crushed into sharp shards of metal or whatever (even bombs somehow work) and from the front it will hose out a massive cone of shrapnel, this can hit many targets for high damage (or massive damage to a large target soaking up all of the shards). If you make a bomb tower feed the Shrapnel bombs, it will spray massive amounts of tiny bombs. NOTE: The damage stat is PER SHARD!