I suspect Mike is talking about "Stover" nuts? (They can be re-used)
Quote from Fastenright Ltd.

Stover Nuts are vibration resistant self locking nuts. Advantages of using the Stover Nut Include:

The self locking function of the Stover Nut is still effective after a number of applications, hence it can be used many times.

The Stover Nut is an all metal Stiff Nut and is resistant to shocks, vibration and dynamic loads.

Stover Nuts is a 1 piece all metal (class 8) nut. The locking function of the Stover nut us achieved by the deformation of part of the nut.

The nut will run smoothly until it reaches the deformed part after which the clamping force will subsequently increase.