A Silver color metal and enamel device 1 1/8 inches (2.86 cm) in height overall blazoned as follows: Gules, a fleur-de-lis Argent, the middle portion formed by a spade bayonet, within and over a lozenge voided Or, cantoned by four fleurs-de-lis of the second. Attached below the device a Silver scroll inscribed “STOPPED BY NOTHING” in Red letters.
The principal colors red and white are for the Corps of Engineers. The old type spade bayonet, forming the middle portion of the large fleur-de-lis, is used to indicate the construction and combat activities of the Battalion. The five fleurs-de-lis represent the European battle honors awarded the Battalion for service during World War II.
The distinctive unit insignia was originally approved for the 51st Armored Engineer Battalion on 9 April 1953. It was redesignated for the 51st Engineer Battalion and amended to change the motto from the French version to the English version on 8 December 1967.