A sentence in past perfect tense denotes that the action of past denoted by verb is completed. It means the work has been finished.
1) 3rd form of verb is used.
2) Helping verb à “had” is used with all subjects.
Affirmative à Subject + had + verb + object.
Negativeà Subject + had not + verb + object.
Interrogative à Had +subject +verb + object ?
Negative + interrogative à Had + subject + not + verb + object?
1) He had completed his work.
2) They had not fulfilled their duty.
3) Had you gone mad?
4) Had we not observed the traffic rules?
5) She had donated the blood.
For practice see