Great tip, Norm. It is probably great for wallpapering.
Another tip for bi-fold doors, where the hardware has gone to the landfill, or should have, a long time ago is to just put regular door hinges on them. I could never get mine to stay in the tracks and when I did, the rod that slides in the top track kept catching on the screw heads. I have now done a couple of closets this way. It is a little more inconvenient to open and close the doors than it was when the tracks worked right, but they worked right so rarely that this is a better way for me.