闸门是坚固的栅栏，位在城门的信道上，必要时可以落下以堵住门口。城堡的城门是一个有内部空间的门房，乃防卫城堡的坚固据点。人们可以透过一条隧道从城门的信道到达门房。在隧道的中间或两端，会有一层或多层的闸门。滚动的机械作用可在门房的上方吊起或落下闸门做扎实的防护。闸门本身通常为沉重的木制或铁制栏栅，防卫者和攻城者则在闸门的两边射击或刺戳。
The gate is a strong fence, which is located on the channel of the gate. If necessary, it can be lowered to block the gate. The gate of the castle is a gatehouse with internal space, which is a strong stronghold for defending the castle. People can get to the gatehouse through a tunnel through the city gate. In the middle or both ends of the tunnel, there will be one or more gates. The rolling mechanical function can lift or lower the gate above the gate house for solid protection. The gates themselves are usually heavy wooden or iron fences, with defenders and Raiders shooting or stabbing at both sides of the gates.
闸门一般由活动部分（也称铜钟 一次性止血带 标志桩模具 钢丝轮 流水槽模具 防撞墙模具 检查井钢模具 不锈钢铸件 模锻件门叶）、埋固部分和启闭机械3部分组成。门叶包括：承重结构、行走支承、支臂、支铰、止水装置、吊耳等。埋固部分包括：轨道、铰座、止水座、护角等。常用的启闭机械有：卷扬式、油压式、螺杆式和移动式机械。
The gate is generally composed of three parts: movable part (also called gate leaf), embedded part and hoisting machinery. The gate leaf includes: bearing structure, walking support, arm, hinge, water stop device, lifting eye, etc. The embedded part includes: track, hinge seat, waterstop seat, angle guard, etc. Commonly used opening and closing machines are: winch type, oil pressure type, screw type and mobile machinery