Deputy Otis - S2-E31
Visible crew/equipment: After Otis admits to Andy the reason why his brother thinks that he works at the courthouse Otis walks back to the cell, but when Andy calls him back and gets up, just as Andy walks around the desk we can briefly see two actor's marks where they will stand momentarily.
Answer: Those "boxes" are valences that used to be very common, before air conditioning. They allow for windows to be open during rain storms. They permit air circulation, without letting the rain in.