Blocking off areas that are not safe for your rabbit is an option. But this is not always possible, if the couch needs to be away from the wall to provide clearance for the curtains, or if there are other concerns about bunny safety.
First position the couch with the desired spacing between the back of the couch and the wall. Decide if an 8, 10 or 12 inch spacing would be optimal. If there is an electrical outlet in the area, decide if it will be used and need to be protected. Identify any other hazards in the area.
I have identified that an 8 inch spacing will work best for me. I want to protect an area 10 foot long. I have an electrical outlet that will be used to run power to lamps at each end of the couch. My previously floor length curtains have been hemmed to just below the window (somebunny started the project and somebody else finished it). My lamps have the electrical cord coming out the side of the base of the lamp.
Materials list; all available at the local DIY hardware store.
8 inch Concrete Form Tube, these come in 4 foot lengths, with nominal diameters of 5, 10 & 12 inches. Each "size" actually is made in 3 measurements +- .5 inch, so the 8 is really 7.5, 8 & 8.5 they ship nested inside each other. I pick 3 (assume one 8 and two 8.5 for this example)
An outdoor outlet cover that will protect the cord while it is plugged in, and has an opening for the cord to exit the box.
A wire cover (maybe called, Chanel, Raceway, Conduit, etc), I prefer the kind where two pieces snap together covering the cord. I did not need corners for this project.
Optional Wood shims. Generally used for spacing/shimming around windows and doors during instal.
With all materials available and the bunnies safely in their room. Pull the couch away from the wall, give yourself lots of room to work. Install the outlet cover. Plug the lamp cords into the outlet and close the covers door.
Measure and cut a length of the wire cover. It will run straight down from the outlet to the floor. Cover the lamp cords, one wire cover may hold both cords (or not) but make sure there is no exposed wires until they touch the floor. Position the lamps where they will be when the couch is back in place with the bare wires laying on the floor near the wall.
In my case the outlet is directly center of the back of the couch. Take the 8 inch tube and place it about center under the outlet. It now covers 2 foot of lamp cord on the floor at either side of the outlet. Take an 8.5 inch tube and slide it over part of the 8 inch tube. You want to have at least a couple inches of overlap, but can telescope the tubes to any length you want. Do the same at both ends (now positioned 8.5, 8, 8.5) as I want a 10 foot section, there is about a foot of overlap on my tubes. The fit will be a bit loose, you can tighten it by inserting some of the wood shims at the joints (but loose is ok)
Slide the couch back into position, it should go firmly against the tube. Position the lamps so the wire coming out of the base is covered by part of the tube that is extending beyond the couch. If the lamp cord can not be covered by the tube, use more wire cover to protect it.
Let the bunnies out!
They now have a safe (and fun) bunny tunnel to explore. Depending on the brand of tube they may chew on the ends of the tube, this fine (ours prefer the taste of the Sakrete brand tubes). A cardboard box with a round hole cut in it, so one end of the tunnel exits into the box will add to the experience (this can be a later addition). The bunnies will run through, hide in and generally enjoy the tube tunnel as a substitute burrow. Ours occasionally try to walk along the top of the tunnel behind the couch. They don't get get traction, and don't tend to try and relax there. The sound when they are walking on top of the tube is rather distracting, but we find it best to let them explore and find their own way off.
P.S. These tubes also make fun toys rolling loose on the floor, they are less expensive and healthier to chew on then the tubes you can purchase at the pet store.
Per the MSDS for SAKRETE FORM TUBE The tube contains no hazardous components as defined by OSHA 29 CFR 1910.1200