Those boxes you'll find underneath the cab and trailers of larger trucks have a very useful purpose. Here's what they're for and what you'll find in them.

Give the box a firm shake to test for wobble; it should feel like it's part of the truck. Should it move, recheck your anchors and tighten again until the issue is resolved.

Give the box a firm shake to test for wobble; it should feel like it's part of the truck. Should it move, recheck your anchors and tighten again until the issue is resolved.