100m card of 40 weight soft tacking (basting) cotton by Naska, 'Fujimusume' label, ideal for all your tacking (basting) needs, in white (first photo). Also available in 420m skeins in pink, Saxon blue, and yellow. 

NB - this is not sashiko thread! Please see my other listings if you are looking for that.

I still prefer to tack my quilt sandwich by hand, rather than using quilters' safety pins, which can leave tiny holes in your fabrics. It is the perfect thread for holding two or more layers together for making sashiko hanafukin cloths, for tacking fabric to templates in English paper pieced patchwork, and many other sewing tasks.

Real tacking thread breaks more easily than standard sewing cottons, so it is easier to remove without damaging your project fabric. I learned my lesson when I was a student, thinking it was OK to use oddments of sewing thread to tack, and accidentally ripped the fabric when taking it out...! Since then, I have always used proper tacking thread.