Ripstop/Tearstop canvas or summer sheet means that there is a stronger, usually polyester, thread, woven into the warp (material length) and weft (material width) of the material at certain intervals. These intervals will vary depending on the textile manufacturer and style of material. This gives the rug not only extra strength but because of the addition of the polyester material makes it more durable. Skye park Tearstop rugs do not give off a static zap like pure polyester materials.
Because of the stronger threads this does not mean the rug is tear proof, as no material is when matched against 500+kg of horse. It simply means that should your horse rip its rug that the rug will stop ripping at the ripstop thread once the reason the rug has ripped is removed. That is, for instance, if a horse catches its rug on barb wire, the rug may rip as long as the horse is rubbing on the barb. When the horse stops rubbing the ripping will stop at that point and not continue to rip under its own weight.