The leaders on my Gammill are thick canvas, and heavy. You do need something heavy and thick so it won't wrinkle over on itself and so it will stay smooth and straight.
A word of advice from experience: prewash and shrink your fabric so later you can spot clean if needed. Mine weren't prewashed/shrunk and spot cleaning made a wrinkly spot-shrunken mess. I had to remove the leaders and wash/shrink them to re-straighten and re-smooth them. It was a HUGE undertaking. I thought I'd never get done ironing them to get the wrinkles out.
Last edited by JustAbitCrazy; 05-26-2015 at 06:51 PM.