two-by-four

US /ˌtuː baɪ ˈfɔːr/
UK /ˌtuː baɪ ˈfɔːr/
"two-by-four" picture
1.

a piece of lumber with a rectangular cross section, nominally 2 inches by 4 inches, used in construction

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He used a two-by-four to brace the wall.
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The frame was built with several two-by-fours.
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studlumbertimberplankbeam
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four-by-fourfourtwofour-wheelerpetit fourplus foursback four