IPA: /ˈɡɑːrdhaʊs/
KK: /ˈɡɑrdˌhaʊs/
A building where soldiers stay while on guard duty or where military personnel are held for minor offenses.
The soldiers reported to the guardhouse before their shift began.
Guardhouse → It is formed from "guard" (from Old French *guarder*, meaning to keep watch or protect) and "house" (from Old English *hus*, meaning dwelling or shelter). A guardhouse is a building where guards are stationed to keep watch or protect an area.
Think of a place where someone is 'keeping watch' ('guard') in a 'shelter' ('house') — that's what a guardhouse is.