How to unlock a thread?

[stochastic]

This may sound stupid, but after locking a thread, how to unlock it?  I was going to lock 2 threats of a security in the Marketplace but did one that I did not want to lock.  Then I could not find a way to unlock it.

[John (John K.)]

move topic  |  remove topic  |  unlock topic  |  set topic sticky  |  merge topics

There's that option below the topic.
Oops, that's for mods only. Try going in the edit option and untick the Lock topic flag.

[EnergyVampire]

I believe you are right, John.

The Unlock button is on the lower left hand side of the thread.