The Mini Nut Knot Nibbler is made by Super Pets, one of my favorite companies for small animal feeders, toys and supplies. This costs about two to three dollars and is more than worth it if you have animals that love to chew. It can get a little messy if there are two or three of them going at it at once but that's when you can see the teamwork that they are capable of.
Some small animals have an almost constant need to chew on things. Part of that stems from their natural instinct and partly because their teeth are always growing. Guinea pigs and rats are two of the small animals I have had a lot of experience with and I know first hand that if they are left to their own devices, eventually they will start chewing on things that they shouldn't.
Rabbits are also known gnawers; I had one that ate through cable wires for the stereo as well as the cord on a vacuum cleaner, the rubber numbers off of a remote control and the wooden base boards behind the couch. That all goes with my steadfast belief that small animals can live peacefully outside a cage and they are happier when they have a choice of whether to be inside a cage or running around freely.
If you are going to allow animals to roam freely within your home you have to make sure it is safe for them and past of that is making sure that you have toys for them to play with. Along with that comes chew toys; this will keep them from chewing on your personal belonging and satisfy their natural need to chew. I was given several of the Mini Nut Knot Nibblers by my veterinarian; he calls me when people abandon small animals and I foster them until I can find a good home for them. Some are not used to human interaction and need to be 'shown the ropes' by other pets. The guinea pigs are the ones that usually boss everyone around and will not hesitate to nose butt an animal that isn't playing along with the game plan.
The Mini Nut Knot Nibbler is an ingenious chew toy; it is a series of wooden rods with smaller rods holding them together. Inside the assembly is a nut. To most small animals that is the holy grail of treats. The Mini Nut Knot Nibbler is safe for pets to chew on and once they get to the nut and break it free they usually keep on chewing on the wooden rods. If you purchase several of these you can change the design or reuse pieces that they haven't chewed on. Varying the design will keep them occupied and give them something constructive to do when you aren't around or can't play with them. So far the rats, rabbits, guinea pigs, ferrets and chinchilla have all enjoyed playing with this but the chinchilla doesn't chew on it, he prefers to push it around or try and flip it.
I would rather spend a little more on this type of toy and have them entertained than to just buy wooden chew treats for them. Not only are they satisfying their need and desire to chew but they are working down their teeth, getting some exercise and having a blast trying to get to the nut in the middle of the Mini Nut Knot Nibbler.