Common Lumber/board Dimensions (in Inches)
Puzzle 20 of Same Letter at Both Ends Easy Pack
Question is: Common Lumber/board Dimensions (in Inches)
and the answer is: TWOBYFOUR
Word Meaning:
TWO BY FOUR — (chiefly Canada, US) A length of sawn wood of cross section nominally 2 inches by 4 inches (actual dimensions 1½ × 3½ in modern use), most often employed as structural framing lumber (dimensional lumber).
Definitions from Wiktionary.