The belt buckle is actually a cleverly disguised zipcord that shoots out a thin, tensile line capable of supporting the weight of an adult human of average size. When the line is fastened to certain, suitable clasps or hooks, the device's miniature motor will lift you automatically.
In Game UseEdit
The Belt Buckle is one of the equipment items that Archer recovers after she escapes from Magnus Armstrong in the Chateau Dumas. She later uses the Belt Buckle to escape from a Poison Gas filled room.
When escaping from the Chateau Dumas, Archer uses the Belt Buckle to get down from a stuck Gondola.
Once this item is introduced in H.A.R.M.'s Promise, the player can select this equipment at the start of the mission. There are several previous missions where this item would come in handy, including an apartment window in Misfortune in Morocco and on the loading docks in A Tenuous Lead.
Belt buckle on Wikipedia