The deathclaw gauntlet is the hand of a deathclaw strapped to its wielder's arm to create a weapon of massive melee killing capacity. This weapon is rarely available for purchase and is a buildable weapon in Fallout 3, while in Fallout: New Vegas it remains as legacy cut content.
To build a deathclaw gauntlet, you need a deathclaw hand, a medical brace, a leather belt, 1 bottle of wonderglue and the deathclaw gauntlet schematics. Presumably, the medical brace is the gauntlet around your player's arm, the leather belt connecting the medical brace and the deathclaw hand and also is the object your player is gripping to make the claws hit accurately where his blow is struck, and the wonderglue helps hold it all firmly together. Although there seems to be screws holding the deathclaw hand in place, they are not needed for building the gauntlet.