This standard covers devices whose primary function is the retention of fasteners@ except for such devices that are integral with the item being retained. The practices cover the types of retaining devices described in the following sections: a. Section 3: Safety Wire (used to prevent disengagement) b. Section 4: Key Washers c. Section 5: Cotter Pins Purpose: The purpose of this standard is to establish the requirements and basic principles for retaining fasteners and other parts in aerospace propulsion systems.