Abstract: A jacket for a quick assembly bolt device includes a longitudinal through-hole having a neck section for firmly engaging with an end of a bolt that extends into the jacket. At least one longitudinal slit is defined in a circumference of the jacket, with a perimeter delimiting the at least one longitudinal slit jointing with an end of the jacket at least one jointing point. The jointing point is broken when the jacket is inserted into a bore of a piece of lumber, allowing the jacket to expand outward for firm engagement with a circumferential wall delimiting the bore of the piece of lumber. The longitudinal through-hole of the jacket allows the other end of the bolt to be driven into another piece of lumber.