Note that not all mortise locks are the same inside. I have two kinds of lock mechanisms that look almost identical from the outside but have a slight...
Step 10: Open the lock case.
Beware that several components inside the case may be attached to springs. If you are not careful when you open the case, you will not get a chance to see how the inner workings are supposed to fit together, or worse parts, may fly off into the far corners of your workspace.
Carefully remove the screw while holding the case together.