Rashi: Begin from the end of the city, so [Bavel] will not know, and they will be caught suddenly.

Radak citing Targum Yonasan: Ascend to it from the side.

Radak: At the time that its end comes, come to it.

Malbim: At the end of the task that Hashem will do, then you should come. (Through the angel's writing Belshatzar was killed, and afterwards came the army of Pras and Madai.)

Rashi citing Targum Yonasan: Its gates. There is no similar word [in Tanach].

Rashi citing Menachem: It is an expression of Avus (feeding troughs). Radak - they are the places where they stored grain. This is like "Evus Be'alav" (Yeshayah 1:3), which is where they put animal food.

Malbim: They are storehouses of grain that they put in the Avus to fatten the bulls. (I.e. take their wealth.)

Rashi: Thresh it.

Radak: Trample on it on the Mesilah (path), like they trample on stacks to thresh them.

Radak citing his father: Make hills, like stacks, from the spoils. He holds that every Mesilah is an expression of raising.

Radak citing Targum Yonasan: Finish off its property, like people finish a stack of grain.

Malbim: They piled up the grain in the troughs like stacks. Open them, and eradicate them until there is no remainder.

Rashi: They are granaries.