So I've gotten asked a few times if I could give away my leftover fabric bolt cardboard inserts from the fabric that I sell so that they could use them to put their larger fabric stash quantities on. (and unfortunately since my home isn't a commercial front I can't start having people I don't know over - not that everyone isn't a nice person ;) but you know it is my home, so I've had to say no). So I've just advised them on where to find some.
BUT I realized that maybe others would be interested in knowing where I used to get mine and that they are FREE!
I used to go to Joann a lot. And I mean a lot, like I knew the staff rotations and when to go to get the 'good' cutters and fast cashiers. Anyway. At one point I started talking to them, I think I happened to be there about 5 minutes before they closed and was telling them about storing fabric etc, and they offered me all their left over cardboard bolt inserts from the evening. Score! So I walked out with about 10 of them and happily bolted my fabric at home (this was before I started buying wholesale myself and was buying in bulk from online stores).
So if you are wanting to bolt some of your larger quantities of fabric, probably 2 plus yards, I highly recommend going to a Joann type store and asking if you can have the ones they are throwing (hopefully recycyling) out. They never reuse them. Clearly you probably won't get lucky if you go in the middle of a Saturday and ask them with 20 people behind you waiting to get fabric cut, but if you get them alone, typically at night, then you can score a bunch of them. I did it a bunch of times and it made my life SO much easier. Plus fabric looks super pretty all bolted on your shelf! Or you could probably also cut them in half and make minibolts out of them or of course build roadways for little people :)