Twill strap is indispensable for placing snap fasteners, color snaps and eyes.
You stick it behind or between two layers of latex. Use white if you are going to work with light latex colors, because black shines through a bit. You need zipper glue to prepare the twill band before you can stick it on latex. If you use normal latex glue, it seems to stick, but once that glue dries, it no longer sticks to the twill band, so use zip glue.
Our book explains exactly how to place and apply twill. And of course we also tell you during our latex workshops.