The Gauntlet, also referred to as the Wall in the Middle Kingdom, is the barrier surrounding material reality, separating it from the Umbra. The Gauntlet waxes and wanes over the centuries, and often from location to location, but the last 200 years have seen a stiffening of the spiritual barrier, most likely related to the increasing influence of the Technocratic paradigm.
Different Umbrae have different Gauntlets, that usually overlap (or may be the same thing). The Gauntlet of the Dark Umbra is called the Shroud, while the Gauntlets of the Middle and High Umbra are often simply called "Gauntlets". The Umbrae of Earth are separated from the Far Umbra through a Gauntlet-like phenomenon called the Horizon.