Anti-submarine weapon used by surface ships during WWII. A
mulitiple spigot mortar, that fired 24 explosive charges with contact
fuses, in a circular pattern in front of the submarine hunter.
Minefield clearing weapon. A variation on 'Hedgehog', fitted to
landing craft. The projectiles were fitted with 20in fuses, to detonate
mines on the beaches by their blast.
I assume that by 20 in (inch) Fuzes the shells had extension rods to ensure that they detonated above ground to trigger buried mines.