WeatherTechCargoTech Containment System - Universal Part 8CTK1

Does it work on regular carpet floors or should I use it with Weathertech cargo liners?

How is this secured to the vehicle?

I have a weathertech cargo liner... how do these stay in place? do they actually lock in or are they only held by the items weight? mine slide around

So would these be good for dumbbells given you need weight on them to keep them secure? Seems like a tough shape as opposed to a box, etc.