Although the ridgeline is bound in grosgrain, we strongly advise you to seam seal the inside of the ridgeline seam to avoid potential water leaks in heavy rain. All the App Hammock tarps are made from 1.1 oz Silpoly, which can be sealed with any 100% silicone seam sealant such as Sil-Net.
Before seam sealing, we also recommend cutting off the three grosgrain tabs along the interior of the ridgeline. Trim these off with scissors as close as possible to the ridgeline seam, taking care not to cut the tarp fabric. You can then seam seal right over top of the remaining stub like normal.
If you have any questions, don't hesitate to let us know. Thanks!