Colloquial term for a pawnshop, derived from the fact that 1 + 6 = 7, and 7 can be read as しち, which is a homophone for 質 (pawn). Often used humorously or in casual conversation.
See also: 質屋
He took his watch to the pawnshop.
一六銀行で金を借りる。
Borrow money at a pawnshop.