。
She fastened the door and the window with a slide bolt.
Literal
She [topic-は] doorway and window [object-を] slide-bolt [with-で] fastened.
戸口 ('doorway') and 戸 ('door') share the same first kanji; 戸口 specifies the entryway frame, while 戸 alone is the door panel. さし錠 ('slide bolt, drop bolt') is a traditional Japanese sliding lock — the kind seen on older houses and gates, sometimes hand-forged and considered distinctive 金物 (metalwork). The instrumental で marks the bolt as the means. 締める here means 'fasten, secure,' using the same verb as 'tighten a belt.' Together the sentence conveys careful, methodical locking-up.