卡 (qiǎ) as a verb means 'to block, to get stuck' — it describes a physical jam or obstruction (e.g., a door, a machine, a finger). Unlike 挡 (dǎng 'to block, to shield'), which is a deliberate action to keep something away, 卡 implies being wedged or caught and unable to move. It is also distinct from 堵塞 (dǔ sè 'to clog'), which is used for pipes, roads, or traffic jams.