Do you know what these are?

I am a thrift shopaholic. I can't drive or walk past or even hear of one without stopping in. I am on a first name basis with most of the staff in the local ones.
Well, I was browsing in one on "senior day" when I found these. I am not sure what they are for, but I get new ideas each time I look at them. I noticed the word Mattel imprinted on them. What they were going to be or supposed to be used for is beyond me. I have several more in various shapes.
If anyone recognizes them please let me know what they were meant to be. Just curious.
 At any rate, expect them to morph into such things as tables, walls and anything else that jumps out at me. LOL