ravine, gorge, gap, (kokuji)
硲 centers on a narrow, steep-sided opening in the land: a ravine or gorge. The gap sense extends naturally from that same image of a deep cleft.
硲 is a Japanese kokuji formed by combining 石 (stone) and 谷 (valley) to express a stony ravine or gorge.
A stone 石 valley 谷: picture a narrow gorge with steep rocky walls. That stony cleft is a ravine.
For はざま, imagine a narrow gap between two huge stones where a hazmat team carefully navigates the ravine: hazmat -> はざま.
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