How many types of lockpins are there?

• A. 3
• B. 2
• C. 4
• D. 1

Answer: (B)

Lockpins are categorized into two practical types: spring-loaded detent pins and standard retention pins. The spring-loaded detent type uses an internal spring and a small locking element (like a ball or plunger) that automatically locks into a hole and can be released by pressing a release mechanism. The standard retention type sits in place without an automatic lock and is held by a separate retaining device such as a clip or cotter pin. In typical ML1 maintenance references, these two cover the common applications you’ll see, with variations treated as subtypes of these bases rather than additional whole categories. So, the count to memorize is two.