🔍 Key Concepts

• The purpose and function of the sheet‑metal nut lock shown in views A–E of illustration GS‑0156 • Whether there are any regulatory or standard‑industry requirements to replace this type of lock with other devices (spring, Belleville, or lock washers) • How exam choices that use words like "no longer used," "mandatory," or "ideal substitute" should be treated on USCG multiple‑choice tests

💭 Think About

• Looking at the illustration, does the nut lock appear to still provide positive mechanical locking of the nut without any washers at all? • Do you know of any general rule or common marine‑engineering practice that bans this type of nut lock, or sets a specific torque value where it must be replaced by spring/Belleville washers? • On similar exam questions, which options usually signal non‑standard practice by insisting on a specific replacement part when the original device is already a proven locking method?

✅ Before You Answer

• Verify whether flat or tab-type nut locks are still considered acceptable mechanical locking devices in marine service. • Check if there is any widely recognized rule that at 25 ft‑lb torque you must switch to spring washers. • Consider whether any option implies replacement is needed even though the existing locking device still performs its intended function; ask if that seems reasonable.