A dock board bridges a gap or height difference the same way a fixed leveler does, but it's portable, no pit, no installation, just positioned wherever a truck backs up without a permanent leveler, or as a backup when the fixed equipment is down. Steel boards handle heavier, higher-cycle traffic; aluminum boards are lighter to reposition by hand.
Pallet dollies solve a different but related problem: moving a loaded pallet across the same kind of gap without a forklift, using casters instead of a bridge. Both categories are stocked, priced, and sized for standard trailer and dock configurations.