The one on Fig. 5-4 is from Daebu Island, and the one on Fig. 5-3 was made in Oi Island. The one with double blades had long and deeply curved neck with short grip (Table 1). In contrast, water hand hoes have longest grip of all hand hoes, and are used to collect water manila clams. Water manila clam are the manila clams living puddles on mud tidal flats. To catch them, one would have to dig under the puddle, so it seems logical to use the hand hoes with longest neck (Table 1).
Table 1.