I have seen a lot of posts about the America/Speedmaster fork lock not working. They work, but in their own way.
Insert the key and turn it about 1/8 turn anti-clockwise. Move the fork slightly off the left stop, push in on the key and turn it back clockwise.
To unlock it, same thing except let the lock pop out. (might have to pull gently on the key if the lock needs to be relubricated).
