A Silver color metal and enamel device 1 1/8 inches (2.86 cm) in height overall, consisting of a shield blazoned: Gules, a chevronel enhanced in base a ram's head affronté erased Argent. Attached below the shield a Silver motto scroll inscribed "CONSTRUCTIO ET DESTRUCTIO" in Red letters.
Scarlet and white are colors traditionally associated with the Engineer Corps. The chevronel is the same shape as a gable rafter, representing construction, while the ram's head represents destruction. The motto translates to "Construction and Destruction."
The distinctive unit insignia was originally approved for the 348th Engineer Regiment, Organized Reserves on 5 December 1925. It was redesignated for the 348th Engineer Regiment, Regular Army Inactive on 15 August 1942. The insignia was redesignated for the 40th Engineer Battalion, with description and symbolism revised on 5 November 1991.