From a legal viewpoint, SGs can be guarantees in the narrow sense but they may also take the form of contractual undertakings (under the PPP contract or other project agreements), indemnity letters or even letters of intent. Setting aside the legal aspects, SGs can be categorised into types of instrument. This section reviews the most frequently used types of SG and is not intended to be exhaustive. Also, SGs are not necessarily mutually exclusive, they can be blended as part of a support package for the benefit of lenders and/or investors.