external door的用法和樣例：
例句
- And as Peter knocked at the door of the gate, a damsel came to hearken, named Rhoda.
彼得敲外門，有一個使女，名叫羅大出來探聽。 - The outer door is a polyurethane foamy one with a glazing unit observation window, for better perspectivity and heat preservation.
外門為聚氨脂發泡門，中空玻璃觀察窗，透視性好，保溫性能好。
