paper holder; paper clip
A clip or holder for temporarily binding papers together; can refer to various types such as a bulldog clip or a simple paper clip.
I put the documents together with a paper clip.
この紙ばさみは厚い書類もしっかり挟める。
This paper holder can firmly hold even thick documents.
Common spelling using kana for the second part, avoiding confusion with 挟む.
Kanji spelling also used, but less common than 紙ばさみ.
Compound of 紙 (kami, 'paper') and 挟み (hasami, 'clip, holder'), from the verb 挟む (hasamu, 'to hold between'). The spelling 紙ばさみ is common to avoid confusion with scissors (鋏, hasami).