This seems like a better place to discuss this topic... Edge-line We are using 11mm static rope (Highline mfg). This reason for 11mm is mainly for the climb (jug) when we frequently tandem; as seen in the picture that Hank posted (Molten Nylon thread http://canyoncollective.com/attachments/greatarch-jpg.3942/). Keep in mind this fat rope weighs in around 45lbs alone, at this length. The Edge-line is basically a utility line and serves multiple purposes; a few not so significant but at least one quite significant. It always has a stopper knot. It should always be marked, flagged or be a different color for easy identification. We don’t always rig one but at certain depths it’s value is intensified. Nice to have purposes: Setup and rope pad maintenance Cleaning the route of loose stuff (where the edge typically gets more foot traffic) Great perspective for capturing cool photography All-purpose safety line at the edge Significant purposes: When working the lip on-rappel it becomes a viable alternative to the mainline. The downside is having to transfer to the mainline once over the edge. The most significant reason for an edge line is to assist the top partner in a tandem climb. This climber has the weight of the rope and his partner below on the mainline. So, crossing the edge becomes extremely difficult (almost impossible). With an edge line the top climber transfers off the mainline and is able to easily negotiate the lip without the weight factors. The edge line can be seen in this picture: Mike is rigging in for rappel on the mainline while Perry is providing slack. The edge line is the blue rope on the ground.