How can I give support to a 20 foot paper mural?

It is 20 ft high x how wide? Did you want to put it on a wall, or what were you hoping to do with it?

How do you want to display it? How about taping to foam core poster boards from the dollar store?

My daughter makes murals every month for the Children's Ministry. She gets 1" thick foam wall insulation panels at Home Depot or Lowes. They are very inexpensive....something like $5.00 a panel. It's 4' x 8' x1" You can cut it any size you want with a bread knife. She covers it with brown butcher paper or white paper and it works like a charm. Knowing the dimensions would help. To piece together two pieces to make it 20 ft, I'm sure duck tape would hold it together before they are wrapped in paper.

It will be important to staple it to the wood securely so that gravity will not pull down the weight of the paper and cause it to rip where the staples are.

First I would lay the mural flat and with duc tape carefully tape around the outside of the mural all the way around all four sides of the mural (making a sort of a frame with the duc tape). Pay attention to getting the tape as straight as possible and an even depth to the edge of the paper to ensure that it hangs level.

It will probably be easier if you had someone assist you at this stage, to have another pair of hands, to keep the paper from lifting up and sticking to the tape before you are ready to stick it down flat.

This will provide not only support, but will also help to protect the paper, as you will have a stronger edge surface to hang on to, and a firm surface for the staples to go into. I would also use a heavy duty stapler, not just a regular desk stapler, to ensure that the staples are strong enough and long enough to anchor into the wood.

You're welcome. 'Hope everything goes well with the project.