When you contact a Locksmith they will ask you what type of lock it is. This can be confusing to some so here is a small list of the basic types. This may help you identify your lock and pass the information to the locksmith.
Yale Nightlatch

Comes in different shapes and sizes but all very similar.
Nightlatch

Comes in different shapes and sizes but all very similar.
Euro Cylinder

Euro Cylinder Thumb Turn

Oval Cylinder

​Also Avaliable as thumb turn.

Mortice Lock

Standard type lock.