four by two

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun UK, New Zealand A length of sawn wood of cross section 4 inches by 2 inches, most often employed as structural framing lumber.
• noun UK, military A cotton cloth 4 inches wide with lines two inches apart, conveniently torn into two inch lengths for cleaning a rifle barrel using a pull through.
• noun Cockney rhyming slang A Jew.