This is the 13518th most frequent Turkish word.
koydukları
"Things they placed/put."
Here, 'koydukları' functions as a relative clause modifier for 'raf', indicating the action of placing the books onto the shelf.
Kitapları koydukları raf çok sağlamdı.
The shelf they placed the books on was very sturdy.
In this sentence, 'koydukları' describes the energy they invested or placed into the lesson.
Derse koydukları enerjiyi farklı projelerde kullanabilirler.
The energy they put into the lesson can be used in different projects.
In this case, 'koydukları' relates to the artists putting or displaying their works in the exhibition.