Single-sided fusible. I gave this stuff a thorough road test whilst writing my bag making book and I absolutely love it! It made my clutch bags firm and boxy; my travel bags sturdy and substantial, and I even used it to make fabric cut-out bag handles. It's lightweight, slim and it bonds to fabrics extremely well. Creases & scrunches iron out beautifully (which is great for turning right side out). Try it as reinforcement for the backs of purse locks and magnetic snaps. On a medium setting, steam iron the shiny side straight onto your fabric for 6-8 secs on each part.
For a general guide to Interfacing/Interlining click here.