Our suggested name for this product was the RoadRage, but still… GridLock is not bad. Black Diamond's newest screwgate biner is 2.6oz of hot-forged, I-beamed shiny-shiny made especially for the belay slave in your life. Biner makers are really pushing the envelope these days in an attempt to innovate and differentiate, so here you are.
The GridLock's innovation is the funky gate, which makes the biner look like a figure 8 when closed. At the halfway open point you can slide your harness belay loop all the way into the small basket, put your belay device – BD hopes you'll use their new ATC Guide – keeper cable in the large basket, and when you close the gate everything is locked into its proper place. The idea is the carabiner can't turn 90 degrees and get cross-loaded, so the load stays on the strong axis as God and Yvon Chouinard intended.
Is cross-loading really that big of a problem? We dunno, but hey, a little extra margin of safety is always welcome. Speaking of safety, one small detail: the edges on the bottom of the gate where your belay loop would rub against it are kind of sharp, but under load it moves away from your body anyway.
Funny note: we were comparing the GridLock to an old BD Pearbiner, and the moving sleeve that locks the gate looks like it hasn't changed in the last fifteen years or more. I guess it's like what they used to say about the door on the Porsche 911 not changing for decades: if it works…