I recently purchased both a 95 and a 96 Blazer and both had these two parts sitting in the back cargo area. Both also had the spare tire in the cargo area as well, so I'm thinking they are related. I'm pretty sure this is going to be something obvious, I just missed it.

 

Thats the hold downs for the jack. And I think the double as wheel ***** if need too.

 

Ah, I see now. I suppose if I would have read the insert in the jack compartment I would have realized that they are the wheel chocks. Thanks Peco.