sheep
The sheep for sacrifice were brought in here.
( See Scofield) - (John 5:2).
tower
The towers appear to have been on either side the sheep gate.
Related Commentaries of Nehemiah 3:1
Nehemiah 3:1
1 Then Eliashib the high priest rose up with his brethren the priests, and they builded the sheep gate; they sanctified it, and set up the doors of it; even unto the tower of Meah they sanctified it, unto the tower of Hananeel.