|11/1/04: I added a link to a picture of the package and the following explanation of what it is:
Wash-a-way Wonder Tape is a double stick tape that is water soluble. For pocket application, for example, you stick one side of the tape to the pocket wrong-side edge, pull off the backing tape, and stick the pocket to the garment. It washes out in the laundry. *However*, as StitchMD noted, it leaves a little bit of white residue behind (but I haven't noticed that the actual adhesive stays around, just a kind of white lint). I've found that you can remove the residue by gently rubbing on it. I imagine that scotch tape or packing tape would also help to take it off. I've found that subsequent washings won't remove the white stuff entirely, you have to remove it by hand. If you apply it carefully, however, as MaryBeth noted in her comment below, it won't be noticeable by anyone except you.
Over on the message board, we listed some of the ways we use Wash-a-Way Wonder Tape, and I thought it would be a good idea to put it here, since not everyone watches the message board.
* Basting in zippers
* Basting on pockets or appliques or waistbands
* Making your machine emb hoop sticky on the bottom so it grips the fabric when you go to hoop it
* Stabilizing and basting hems or seams across the stretch of a knit fabric.
* Holding trim in place for stitching
* Basting slippery fabric
* Matching plaids or prints
* Holding a button in place while you sew it
* Emergency hem repair
* Holding those "turn under seam allowance and top stitch" projects
* Keeping appliques in place while they're sewn (hand or machine)
* I do quite a bit of sewing with fleece and I use it to insert zippers and also so hold bulky seams together when the long daisy head pins won't do the job
* Fixing the gaposis on button down blouses.
* Sticking bra straps to blouse to keep the #*#(# things from falling down
* Hold shoulder pads in place until they can be tacked in
* Hemming napkins, dishtowels, placemats. Wonder tape gives an exact 1/4 inch doubled hem
* Use it anywhere that's likely to stretch or shift badly
Courtesy of DebJCook, StitchMD, Diana M, BorderCollieMom, Sherrill Miller, Lizz, and Cornelia