sprag
/spræg/noun
1
- a simple brake on a vehicle, especially a stout stick or bar inserted between the spokes of a wheel to check its motion制轮木（插在车轮辐条之间的棍棒, 用以防止车轮滑动）。
2
- a prop in a coal mine煤面防护柱; 煤矿矿井中的支柱。
词源
mid 19th cent: of unknown origin.