What is the purpose & how do you use those permanent (metal?) charcoal briquette shaped things for grilling?!
Answers: If you're talking about for a gas BBQ grill, they're actually lava rocks. They go above the flame but under the grill that holds the food. They distribute the heat evenly and do much the same thing that charcoal does in a charcoal grill, only they're not messy.
You got me---I'll only use a charcoal grill.
The flavor is the best.