I found this little peice at Walgreens. I only paid 59 cents for this, and all I used was 4 zip ties to secure it. As you can see Turbo wasted no time checking it out.
I use it for a veggie tray. ^.^ Make sure you have a couple of them if you have more than one guinea. My girls have two, while my boys both have one of their doors. I was also tempted to use one as a small hay holder in the other part of my girls cage, but i figured it would be too messy since it's fleece.
I have the same one! We also have a piece of board behind it so the hay doesn't fall out the back of the cage into the kitchen. We fill ours 3-4 times a day (when it's halfway empty) and give him a handful on the floor to mess around in all day.
And that is exactly what my timothy hay from Oxbow looks like (highly recommended by this site), to whoever commented that yours looks hard. My piggie doesn't like it.