The Grigri's primary advantage lies in its ability to catch a falling climber more effectively than the ATC. It reduces the risk of belayer error, making it a reliable choice for climbers of varying experience levels.

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Rappelling with the GRIGRI can be done on EN 892 dynamic or EN 1891 low stretch rope of a compatible diameter indicated on the device. There are several ways to set up the rope for rappelling: they are described in the technical tip, Multi-pitch rappelling with a single rope.

Daughter is using a Grigri as a self-belay device. This is expressly discouraged by Petzl, the manufacturer, on this page titled Self Belaying is Prohibited. That's pretty damning. As the page admits, some people do use a Grigri for self-belays, but it's not ideal and potentially dangerous.