Occassionally you will need to stop part way down a rappel. This could be so you can take pictures, so you can adjust your gear, so you can rescue someone, or so you can reach something. The method you use to lock off your rappel device depends on the type of rappel device you have. Some devices are really easy to lock off, but others can be very difficult. I recommend that you become proficient at stopping mid-rappel using whichever devices you will be using most often as well as with a Figure 8 and an ATC.