Japanese by Example
Learning through examples in manga

Only the ace of spaces with 〜だけ

名探偵コナン » Volume 12 » Page 20

The Detective Boys group visit a cabin where Professor Agasa has secretly set out clues leading to a treasure. Conan draws the group’s attention to an arrow pointing to a table, on top of which there is…

"A pile of cards, rather unnaturally scattered about."
"Further, for some reason, only the ace of spades is pinned down with thumbtacks..."

だけ limits the subject pinned down by thumbtacks to 「スペードのA」.