expression, godan verb (-ku)
reserve a seat; book a seat
Literally 'to take and put a seat aside', i.e., to reserve or hold a seat for someone. It is a rare term; in modern Japanese, 席を予約する or 席を取る are more common for booking, while 席を取っておく can imply holding a seat informally.
いい席を取っておいてくれてありがとう。
Thank you for saving a good seat for me.
コンサートの席を取っておくのを忘れないで。
Don't forget to reserve seats for the concert.