A slang term for the insignia worn by a Specialist (an E4 in the Army not qualified in leadership ability to be a Corporal). Refers to the ability of persons of that rank to sham (get out of work or other responsibilities)because of there rank being not yet that of one expected to know their job completley or be dependable. Those wearing the "Sham Shield" are known for their uncanny ability to come up with ludacris excuses for getting out of even their few responsibilities.
Sgt McClanahan: Cpl Hardcharger, do you know why Spc Shitbag didnt complete his duty log.
Cpl Hardcharger: Sgt McClanahan, Spc Shitbag said that he was excused from extensive writing as per his light duty chit.
Sgt McClanahan:I should have known it wouldnt get done as soon as I saw him sporting the Sham Shield.