Attachment Point
Before we start rappelling, we first need to approach the anchor station, either by using a Traverse line or just by walking to it. An anchor station would be at most times located near the edge of a cliff or a waterfall. This means that while we are preparing for our descent, rigging the rope to our descender etc, we will be standing very close to a potentially dangerous cliff edge.
The master point
Therefore it is vital that as soon as we reach the anchor station we clip our lanyards securely and then proceed with the rest of our descent preparation in full safety. In order to make the process easier, there will be a Master Point (or Master Carabiner), attached in a visible and easily accessible point of the belay, where we should clip our lanyards to. The placement of a Master Point makes moving around the anchor station much safer and efficient, as people know immediately where to clip into without needing to search for a spot or worse, by staying unclipped for the time they are standing by the anchor station.
The Master Point is usually a large locking carabiner attached to a high point in the anchor station, so as to be visible and able to accommodate multiple attached lanyards. Once we arrive at the anchor station, we check that the Master Point is locked and then we clip one or both of our lanyards into it and lock them as well. Then we are ready to proceed with our preparation to descend.
Here’s a video demonstrating the technique: