I have an angora rabbitry and wanted to allow them access to the grass beside the cages and the ability to stretch their legs. I used to pick them up out of their cages and physically bring them to the enclosure, quickly shutting the gate behind me. I was sure there was a safer method so made them a habitrail (or rather a rabbitrail) instead.
Step 1: Make a Door
it's difficult to see from the picture, but I had to make a door on the end of each of the cages. I cut a piece of wire grid big enough for them to exit to serve as the door and cut the hole in the cage slightly smaller than the door. Secured the door with wire at the bottom to serve as a hinge. The doors are secured at the top with dog clips, and their water dish has two hooks on both corners to further secure the door in the event that one of the clips isn't properly secured.
Step 2: Find a Large Tube and Cut a Section Out of the Top
I polled folks on craigslist to find a suitable tunnel. The one I found is 15.5" in diameter and was about 20' long. The person I spoke to agreed to cut it into manageable lengths so I could put them in my truck. The PVC tube was very thick, so I cut a great deal out of the top to reduce the weight, allow ventilation and permit the rabbits to see above it. The tube was given three legs and was set at an angle to prevent the tube in step 4 from being too steep. I lined the tunnel with a strip of carpet to prevent the rabbits from slipping. (The wood structure to the right is an add-on cage I made when the new litter was big enough to need the space.)
Step 3: Enclose the Tunnel With Chicken Wire
I drilled holes about 2" apart the entire length of both sides of the tunnel. I wired the cage side of the tunnel to the cages to prevent the tunnel from separating or shifting, and I added chicken wire over the tunnel and "sewed" it both to the outside of the tunnel as well as to the cages above the doors.
Step 4: Add the Ramp
A small section of tubing was placed at an angle to the cut tunnel to allow a ramp down to the grassy area. It has a foot to secure it on the right. I had to cut a hole in the chain link fence to allow the tunnel to extend beyond the kennel. I put another piece of carpet in the tunnel and secured it with screws and enclosed that with chicken wire as well.
Step 5: Make the Enclosure People Proof
I stood the rigid green fencing on end and wired it to the kennel to allow the enclosure to be people-friendly, I used bi-fold doors and lattice which were roughly the height of the green fencing. Those were wired to the chain link fence between my property and the neighbor's.
Step 6: Testing...
As you can see, fluffy bunny can get down to eat the grass.
Step 7: Add Piece of Mind
It's difficult to see, but there is wire laid the entire length of the grassy area and lapped up the side about 2' to prevent the rabbits from digging out. I also attached that wire to the top of the lattice and rigid green fencing to prevent the hawks from having a rabbit dinner. I will eventually put dirt on top of the wire fencing as it would be possible for a rabbit to trip on the fencing as they run, but for now, it is rewarding to see the rabbits enjoying themselves and eating the grass in the enclosure.