These are the Fiskars texture plates, they are used together with the little blue tool on the photo to help create texture on cardstock.
I've had these for quite a while now but have rarely used them because:
1 - I find it difficult to use the little blue tool. To create texture you need to place the piece of cardstock on the texture plate and then using the tool make circular movements to emboss the image. I could never do this for long anough because my wrist started to hurt after a while;
2 - I could never get a clear and crisp embossed image.
Now, I found a way of using them to emboss cardstock and obtain a nice, crisp texture as shown in the photos below.
The light blue cardstock was lightly sanded after embossing to create that wave foam effect.
If you have some of these Fiskars texture plates and a Sizzix BigShot this is how you can use them to emboss cardstock.
You'll need:
Sizzix BigShot
Fiskar texture plate
Sizzix multipurpose platform
Cutting pads
Foam sheet
Cardstock
Make a sandwich with all the items above in the following order:
Multipurpose platform (use no tabs)
First cutting pad
Texture plate
Cardstock (make sure it's aligned over the texture plate)
Foam sheet
Second cutting pad
Run this through the BigShot to emboss your cardstock.
This is one of a series of flowers I made with cardstock embossed this way.
Have fun experimenting with your texture plates 
