This is the 12058th most frequent Russian word.
зубчиках
"Зубчиках" is the prepositional plural form of "зубчик," meaning "small teeth" or "cloves" (as in garlic cloves).
Here, 'зубчиках' refers to the format in which garlic is grouped, emphasizing individual segments as 'cloves'.
Я купил чеснок в зубчиках.
I bought garlic in cloves.
In this sentence, 'зубчиков' is metaphorically describing the shape of the chalk pieces.
На доске были разложены мелки в форме зубчиков.
On the board, chalk pieces were laid out resembling cloves.
Here, 'зубчиками' refers to the crenelated (notched) structure of the castle's wall tops.