This is the 15055th most frequent Russian word.
позакрывали
"Позакрывали" means "closed multiple things (they) completely" in English.
In this sentence, 'позакрывали' uses the verb 'закрывать' in the perfective aspect to describe the complete action of closing all the windows.
Они позакрывали все окна перед сильным дождём.
They closed all the windows before the heavy rain.
Here, 'позакрывали' emphasizes the action of putting all their toys away in a manner indicating that the action is cumulative and finalized.
Детвора позакрывали свои игрушки в коробках.
The children locked away their toys in the boxes.
In this case, 'позакрывали' underlines the collective completion of closing all documents as part of preparing to finish the task.