纸上封锁

例句：

1. 1. The government has sealed off the border to prevent any further incursions.
   政府已经封锁了边境，以防止任何进一步的入侵。
2. 2. The seal on the envelope is unbroken.
   信封上的印章完好无损。
3. 3. The seal of the kingdom was placed by King Arthur.
   亚瑟王在王国上刻下了印章。