句子加左ed是形容詞定簡單過去式

1. No entry unless (authorized)= No entry unless it is authorized by someone.
The verb (authorized) here is a past participle used as a verb in the passive voice.

2.pavement (closed) can be expressed as this pavement is closed.
The verb (closed) here is also a past participle but used as an adjective.

I give you a further example here. This vase has been broken by the dog, luckily my father knows how to repair the broken vase. The first verb (broken) is a past participle used as a main verb in a passive sense. The next verb (broken) is also a past participle but used as an adjective to qualify the vase.
I hope that the above can solve your problems.

睇下你係將個詞放係咩句上面,好似你話'that store has closed'即係過去式,相反'that store is closed'即是形容詞