Step 1: The first cut is the deepest.....
*a t-shirt (sleevless/vests type works best)
*bootlace or other strong cord thats long enough to go round your waist
*drawstring toggle (i never throw stuff out so had one off an old rucksack, but you can buy them in craft stores)
find the hem and snip open the side seam (about 1cm) to open this channel
Step 2: A stitch in time.....
-this will make threading throuh the hem MUCH easier
feed safteypin&lace through the hole you have just cut in the hem
feed all the way through so the lace runs through the whole length of the hem
Step 3: Gather
pull tight gathering up the hem
Step 4: Voila!
take off shirt (hopefully you are not now naked!)
gather in drawstring tightly
fill bag with shopping
go home, rejoicing in your eco friendly credentials
get home, empty bag
launder shirt (this will help it back into shape)
you are ready to face another day of impromptu shopping dilemmas!