be (as) thick as thieves

To be very close friends. Anna and Beth are together all the time these days—they're as thick as thieves.

Name	Pronounced	Usage
Ron (2)	-	Hebrew
Branimira	-	Croatian, Serbian, Bulgarian
Vincentas	-	Lithuanian
Enoch	['i:nɔk]
Baldick	['bɔ:ldik]
Tania	TAHN-yə (English), TAN-yə (English), TAH-nyah (Italian)	English, Italian