Also known as a unit crest or DUI, the Distinctive Unit Insignia is worn by all Soldiers (except General Officers) in units that have been authorized to be issued the device. It is worn centered on the shoulder loops of the Army Green Service Uniform (AGSU) and the blue Army Service Uniform (ASU, Enlisted only) with the base of the insignia toward the outside shoulder seam. DUIs are not worn on the Dress variations of either uniform, however.
Full guidance on wear of the DUI is found in DA Pamphlet 670-1,
Section 21-22, "Distinctive unit insignia."
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“One Team, One Fight” forms the foundation of the Distinctive Unit Insignia of the Special Troops Battalion, 4th Brigade Combat Team, 3rd Infantry Division, approved for the “Sentinel” Battalion on 14 September 2005. Dark blue found throughout the insignia represents Infantry, whose efforts the Battalion support. In the upper left, a gamecock on an orange background symbolizes Signal Corps functions (orange is the Signal Corps color), while opposite it a dragon on an oriental blue field is an allusion to Military Intelligence.
An embattlement in the middle of the shield evokes the Engineer function (the Battalion was formed from the former 3rd Infantry Division Engineer Brigade). A double-edged fasces on the embattlement is a standard theme from Military Police heraldry, representing the functions of security operations, law enforcement, and the processing and internment of prisoners (or sheltering of civilians); the billet between the axe-heads recalls the design of the Shoulder Sleeve Insignia of the Brigade Combat Team’s parent organization, the 3rd Infantry Division.
Activated for less than a decade, the Sentinels of 4th Brigade Special Troops Battalion, 3rd Infantry Division earned credit for participation in two Iraq campaigns, Iraqi Sovereignty and New Dawn, as well as a Valorous Unit Award for its service during its first deployment to Iraq in 2005. The Battalion and/or component units was the recipient of two Meritorious Unit Commendations, the final one issued in January 2014 for its service in support of Operation Enduring Freedom between March and November 2013.