绝缘套管为导体的通过提供缝隙的绝缘套管 An insulating lining for an aperture through which a conductor passes.
鳃盖覆盖在一孔或缝隙上的盖，如一些鱼类的鳃或覆盖在蛇或其它软体动物身上的角质壳 A lid or flap covering an aperture, such as the gill cover in some fishes or the horny shell cover in snails or other mollusks.
