The idea for this hay rack came from a horse hay feeder that I found through Google. https://www.gatortoughranchstuff.com/product/SPAS105#
What I did was bent a grid to form a V shape and attach it to a coroplast box that doesn't have the top and bottom. You can see the red zip ties that kind of look like stitches. That's the top part of the hay rack. The rack can be removed from the bottom tray.
The bottom tray is made from another piece of coroplast and made with higher sides on 2 sides and 4" high on the sides that let the pigs access hay. The the whole tray is attached to grids for support. Then I zip tied the black grid (with the circle holes) to the regular grid to babyproof the side that faces out from the cage wall. I also like the look of the black grid more than the regular grid.
The top part of the hay rack has a large zip tie that I looped through so the top can be clipped to the bottom part.
Does it make sense? If not, I can take some pictures when I take them apart.
You're welcome! The coroplast tray is attached to grids with zip ties. I just puncture holes where I want to attach them. There's a flaw in this design though. The tray is hard to remove for cleaning. I might make a few modifications.