Rashi: It seems to him that all the roads are fenced with fences of Chadakim (thorns). Mesuchas is a fence, like "Haser Mesuchaso" (Yeshayah 5:5).

Rashi citing Tanchuma Ki Sisa 1: Esav's Derech is like a thorn caught in wool shearings. If you take it from here, it gets stuck here. So one cannot evade his pretexts without [paying] money.

R. Yonah: It is a fence of thorns; no one can pass. So an Atzel can only be in back, but not in front, to go from Midah to Midah.

Malbim: Derech is the big road from city to city. Orach goes from the city to the villages. The Atzel is lazy to go. Even on the great path that many go on, he imagines that it is like going on a fence of thorns. It is hard to go on it, for it is a fence, and the thorns puncture the feet of one who goes on it.

Rashi: It is paved and clear.

R. Yonah: It is contrasted to (the opposite of) Derech Atzel. Yesharim are people with a straight heart.

Malbim: For Yesharim, also the path that not many go on it, it is as if it is a straight paved path that is comfortable to go on it. The verse puts Yesharim opposite Atzel, for Atzel is lazy to go in the way of Chachmah. It seems to him that also the fixed path, it is as if it is full of thorns. He thinks that he cannot conquer his desire and go against his Yetzer, and all the more so he cannot go in the individual paths [of Chachmah]. Yesharim, whose hearts are straight and lean towards good, also the individual paths that they go on - Midas Chasidus and Tzedakah - are paved. Desires and Yetzarim of the heart do not fight him, since his heart is straight, like I explained above the difference between Tzadik and Yashar (refer to 11:3:1:2).