also: ホチキスしん
noun
Refers specifically to the metal staples used in a stapler (ホッチキス).
See also: 芯
ホッチキス芯が切れたので、新しいのを買わないと。
I ran out of staples, so I need to buy new ones.
芯 is a general term for a core or refill (e.g., pencil lead, wick); ホッチキス芯 is a specific compound for staples.
Compound of ホッチキス (from the trademark 'Hotchkiss', a common Japanese term for a stapler) and 芯 (しん, 'core').