The Past Participles (Perfect Participles) ends in -ed, -t, -en, and -n.

1. The past participles of transitive verbs are used just as adjectives.

He has no hidden faults.

He looks frightened.

It was well-built house.

2. Generally the past participles of intransitive verbs are not used as adjectives before nouns. But there are exceptions, as shown in the following sentences:

He is a known killer.

They were trained dogs.

Mr. Bruce is a retired postmaster. …