Taco bed has place for wood planks?

I just noticed that on the new 2024 tacos that there is a place in the bed for two 6 or 7 inch wood planks across the bed in niches in the inside walls. Then I went to my 2016 and saw that they were also there. That is embarrassing! What are they for and who uses them?

 

I put a board there once to make some drywall not bend so much.

 

I use them to put 2 2x4s and an attached extension on the tailgate (hard to explain) to carry 4x8 foot sheets of whatever.

 

https://youtu.be/-AOie9-lSww?si=jw3LEWQhsYPar-cS

 

If you don't want to drill into your bed and can get multiple positions you can use 1/4" chain like this--

https://www.tacomaworld.com/threads/adjustable-tailgate-cables-on-the-cheap.477171/

 

Anybody know a related hack for 5 foot by 5 foot baltic birch plywood?

 

4×9' OSB