This spring-fit hook is presented as an alternative to the post “Cross Bar Scan Hook in Plastic.”  Metal hooks of this and similar styles clip onto cross bar, grid, and wire cross bar. The clip-on feature prevents the rotation pointed out in the plastic hook post. It also grips the crossbar and prevents the metal hook from being jostled out of position laterally along the bar.

For a related but plastic style fixture SEE…
Cross Bar Scan Hook in Plastic

For a more atypical Clip-on Plastic Hook SEE…
Plastic Hook Backplate Kaizen for Jewelry