Rashi: They are carpenters who know how to saw the corners. In Sukah 52b, it explains who they are. Radak, Malbim ? they are Mashi'ach ben David, Mashi'ach ben Yosef, Eliyahu, and Kohen (Malki) Tzedek. Malbim ? i.e. in the future the strength, war and Malchus Yisrael (Mashi'ach ben David, and Mashi'ach ben Yosef on the side of the nations) will cut off the Keranos, and also the strength of Kehunah and Avodas Hashem ? Eliyahu on the side of Yisrael, and Malki Tzedek on the side of the nations.

Radak #1: This is like "Charash Etzim" (Yeshayah 44:13). Each kingdom will be like a carpenter to cut off the previous one. Malchus Bavel fell to Paras, Paras fell to Yavan.

Radak #2: This is a Mashal for the Sarim (the angels) appointed over the kingdoms.