Grapple-Gloves are weapons/tools designed by the Autobot scientist Que. They fire a small harpooned dart with a length of high tension wire attached to it. This allows them to be used for climbing.
In the Dark of the Moon film, Que invents many things. One of these things is the Grapple-Glove. The device was first notably used when Que took them out just before the Autobots began fighting the Decepticons in Chicago. When Sam asked what Que's inventions were and did, Que quickly explained the usages of both the Boomstick and the Grapple-Glove. He also said that the glove could be used for climbing. Sam took one Boomstick and one Grapple-Glove.
As Sam, Epps, Carly, and Epp's friends journied through Chicago, they were ambushed by Starscream. Epps and his friends ran into a building, while Sam and Carly ran down an alleyway that turned into a dead end. There, Starscream cornered them and readied himself to kill Sam. However, the dimwitted Decepticon leaned in forward, allowing Sam to shoot the Grapple-Glove's hook so precise that it dug into Starscream's eye.
Starscream began to violently thrash around, in great agony from his eye injury. Minutes later, Sam stabbed Starscream's other eye with the self-destructing Boomstick. Seconds after the Boomstick was shoved into his eye, it blew up. Since Sam was still in posession of the Grapple-Glove at the time in which it had clinged to Starscream's eye, the rope attached to the hook was destroyed when the Boomstick exploded. This not only ended the Grapple-Glove and Boomstick's usages, but it also ended Starscream's life.