I am grateful for my wet canvas carrier. Although I have not used it in a couple years, it came in use a couple days ago!
Stretching my own canvas means that I normally do not install a support bar (unless the canvass is long), and a support bar serves as a good handle in addition to keeping the frame bars from warping.
I am working on a pretty large painting, about 42 inches height, and needed to transport it by foot 1.2 miles, through the wind and hills of San Francisco. I thought about taking the bus, but was worried about crowds and other people on the bus potentially damaging my painting. Taxis are expensive. It took me a while before I realized I still had the wet canvas carrier stashed somewhere.
This thing can be pretty handy from time to time.