Gummed Paper Tape
The gummed paper tape is needed when stretching watercolor paper and when framing. The tape is made of paper and has a gummed surface, which means that you must use water to make it sticky.
There is brown and white tape, the white may be acid-free or not. For stretching, I think the brown tape works best, it is thicker and has more glue, it sticks better, in other words. It is not good for framing, it is not acid-free. For framing, use white, acid-free tape. When stretching, no acid-free is needed (you should not leave the paper stretched for that long). For framing you probably need a narrower tape. For stretching, you need, in order to be sure that the tape does not come loose, 2 inches (5 cm) wide strip.