Rashi: They are the colleagues of the one who formed the idols. They join to him to serve what he formed; they will be ashamed.

Radak #1: They join to him to make [the idol] or serve it.

Radak #2: The idolater is Tohu, and those who engage in it are Tohu, like it - "Yotzerei Fesel Kulam Tohu" (9); they are colleagues of the idol.

Malbim: This refers to idolaters who recognized that the idol itself is nothing, just the worker intends for the form. He makes it at a known time, and intends for known deeds. Afterwards, people gather together and direct their deeds and intents to a particular power from higher forms and their stars, and they will fear these powers. The idol does not bring Brachah to them; it is only due to the people's intent. We find like this in Kedushah - one who acts with intent draws Kedushah on what he makes. Here, they will be ashamed, for their gathering will not help.

Rashi: Those who form and make the molten images - they are from people. All the more so what they make is folly!

Radak: They are not angels who do this, rather, human craftsmen who do other works, and make it a god. This is astounding!

Malbim: The ones who made the idols - they are human. How can they arouse supreme powers?!

Radak: All idolaters will gather and discuss their deeds, and look at it. If they will do so, they will fear Kel for what they did, and be ashamed of their deeds, which are Tohu, when they contemplate it.

Malbim: If the smiths and the others would gather and stand opposite the idol, even if they will arouse themselves to fear (influence from the stars at that time), they will be ashamed, for they will see that their deeds are folly.