Measure the box spring from right to left and find the exact middle point. Mark this lightly with a pencil or fabric marker on the dust cloth.
Cut the dust cloth on the box spring straight across this marked line, using a razor knife or box cutter.
Cut the box spring fabric up the entire side of the box spring, using the razor knife or box cutter. You may mark the line first if you wish, but it needn't be in an exact location; simply on the side.
Repeat this process on the opposite side of the box spring.
Use your saw to cut the wood framing braces along the same line where you cut the dust cloth. Repeat this step along the sides, cutting into the wood frame. Be careful not to cut the steel rod that runs alongside the frame.
Tip the box spring onto its side and begin the folding process. Place the soft side against a door frame or solid and sturdy surface. Have someone stand on either side of the box spring, and firmly folding together, much like closing the pages of a book.
This will allow the box spring to fit up most any staircase.