The Mainsail slides up and down in a track, which is integral to the mast extrusion itself. The sail has several "T" shaped "cars" attached to the leading edge "Luff" of the sail. The cars ride in the track on the mast, and keep the sail affixed to the mast. Some of the cars are sewn on, with a high grade webbing. A much better solution in my opinion.

When taking the Mainsail off, that a few of the plastic slides were broken, as were some of the shackles. Three of the shackles had snapped and shockingly not let loose from the sail. I ordered 10 shackles and 10 slides. I also ordered webbing, in order to see if I had the chops to sew the new cars on. Point of note.... Always check the quantities you're ordering. I ordered 10 of each item. Turns out I ordered 10 packs of 5 of each item. So, I have a couple spares. Moreso since I ended up sewing them ALL on!