The gin - Another method of taking wild beasts. It was a snare so made as to spring suddenly on an animal, securing him by the neck or feet. We use a trap for the same purpose. The Hebrew word (פח pach) may denote anything of this kind - a snare, net, noose, etc. with which birds or wild animals are taken.
By the heel - By the foot.
And the robber shall prevail - He shall be overpowered by the highwayman; or the plunderer shall make a sudden descent upon him, and strip him of his all. The meaning is, that destruction would suddenly overtake him. There can be no doubt that Bildad meant to apply all this to Job.