What were the "Sharsheros"? Where were they fixed?
Rashi #1 (citing Menachem ben S'ruk): Based on the word 'Shoresh' (root), which holds the tree in place, the cords which were forced into the settings at the end of the straps of the Eifod to hold the Choshen in place. 1
Having mentioned the cords in Pasuk 14, why does it repeat them here?
Rashi (in Pasuk 14): This is the main locaton of the cords and the Torah only mentioned them there to explain the purpose of the settings in the Eifod.
Oznayim la'Torah (citing the Rambam): There were actually two sets of cords
See Oznayim la'Torah on Pasuk 14.
What is the meaning of "Gavlus"?