What are these plastic bits?

[Markarian421]

I noticed these on the frame rails on either side. One was smashed. What are they and is there any reason I should possibly care that one is smashed?

 

[PACruiser]

I wonder if they are temporary caps they put on when they waxed the frame at the factory. Good video on build quality from a mechanic's review where he goes over the rust proofing.

The Car Nut LC Review