。
She pinned the medal to her collar.
Literal
She [topic-は] that medal [object-を] pin [with-で] collar [to-に] fastened.
This sentence packs three different particle uses into a single line: を on the medal (the thing being fastened), で on the pin (the instrument used), and に on the collar (the destination of the fastening). That distinction between で-of-means and に-of-target is one of the cleanest demonstrations of how Japanese carves up case roles. とめる (留める / 止める / 停める, all read とめる) covers fasten/secure/stop/park — the kana spelling lets the writer leave the specific kanji ambiguous, with context picking the meaning. Here it's clearly 'fasten / secure'.