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A Grigri (or Gri-gri or Gris-gris) is an assisted braking belay device manufactured by Petzl designed to help secure rock-climbing, rappelling, and rope-acrobatic activities. Its main characteristic is a clutch that assists in braking under a shock load. The success of this device has led to grigri becoming a common name for devices of this type. In 2011 a new version, the GriGri 2 was released. Competitors include the Faders Sum, Trango Cinch and Edelrid Eddy.
Mechanism of operation 
The Grigri works by pinching the rope when it is moving quickly (like in a fall), making it an assisted braking belay device unlike traditional belay devices such as a Sticht plate or an ATC. Internally, the rope runs along a cam, which allows the rope to pass if moving slowly but when the rope moves quickly the cam will rotate, pinching the rope.
Pros and cons of use 
Some climbers[who?] feel that the Grigri is only suitable for top rope climbing and not lead climbing due to the assisted braking feature, though Petzl recommends the device for use in both applications. The claim against usage for lead climbing is that since the device assists in stopping the rope, the belayer often mistakenly holds the device open while feeding rope to the leader. Another common mistake while belaying a lead climber is to hold the device open the entire time, thus defeating the assisted braking mechanism. This practice renders the device entirely useless and has been the cause of many accidents. Users can and should learn how to feed rope without holding the device open. Petzl has released information on how rope should be fed through in a lead climb, including how to let slack out quickly so that the climber can clip a quickdraw on a sport route.
When used correctly, the Grigri's camming mechanism can assist in holding a climber that is working a route, or hanging on the rope while trying to figure out a climb. For lead climbing, a Grigri is more difficult to use correctly than an ATC; for top-rope climbing the grigri can be difficult to lower the climber with. When belaying, the same technique for "taking in" that is used with an ATC or similar device is used. However while paying slack out into the system if the device is held open (with one technique being referred to as "the thumb") and the climber falls, unless the belayer lets go of the gri gri and continues to hold the break rope the device will not lock and the climber will hit the ground.
The Grigri is heavier and more expensive than other belay devices. Many climbers aim to reduce, as much as possible, the weight they carry on climbs. However, there are applications where only an assisted break belay device will work. The Grigri has a lower limit for the rope size for which the cam will engage. This makes it unusable with many of today's skinny ropes - like those used in many alpine applications.
Big wall use 
While designed as a belay device, big wall climbers have invented novel ways to use the Grigri that are not recommended by the manufacturer. For example some big wall soloists use the Grigri (sometimes slightly modified but not necessarily) as a self-feeding hands-free self-belay device. In big wall situations, the Grigri allows for hands-free belaying on long aid pitches while the rest of the party does other things. It can also be used by the second to self-belay while jumaring the rope as one half of the ascender pair; the leader can belay the second hands-free allowing the leader to haul, take pictures, or do other chores; the second can use it to lower out while following a traverse.