Designing with Lily Lines French curves is easy and endlessly fun. This short, free PDF design prompt will get you started. It is perfectly safe to use a permanent sharpie marker on the smooth side of the acrylic rulers, as long as you remember to wipe it off when you are done designing and not leave it long term. I keep individually wrapped alcohol wipes in my studio for this purpose. You can get them at any drug store or pharmacy department. Align the precision markings with a grid line registration mark in your design. You can stitch and flip your way around your design to create beautiful frame elements, feather foundations, and block designs.