This is a piece of climbing apparatus that allows you to ascend a rope. It is the lightest ascender on the market weighing in at 22 grams. It is produced by Petzel.

The triblock is a long u shaped piece of metal which sits around the rope. There are holes in the sides through which a carabiner can be clipped. As you pull down on the carabiner the carabiner and the triblock squeeze the rope between them gaining purchase on the rope.