You can never be too careful, so even though we have built a trigger brake into the Alien Flier AF-XTreme, you should use a stop block as an added layer of safety. The Alien Flier stop block set encases the cable near the terminal end. When the trolley frame makes contact with the block, the block begins to slide engaging the bungee rigging* which quickly decelerates the trolley, bringing your rider safely to a stop. This stop block installs easily with a few simple hand tools. No home zip line system is complete without a stop block!