Sliding glass door lock.

I'm afraid I can't tell which is broken, either. What exactly is the problem? Does the hook not engage the keeper? Also, is the mortise lock otherwise functional? If so, it's possible the door is out of jamb. I don't think the keeper is the problem since it appears to be in pretty good condition.

Another possibility is that the anti-slam button (that button you see in the dead center of your mortise lock) is not working properly. This button is meant to keep the hooks retracted until the door is closed. If it's broken or stuck, for whatever reason, then the locks would remain retracted even after you close it. Is that the problem you're having? Knowing as much about the problem as possible will be a huge help. Please don't spare any detail.

Assuming you need a new internal mortise lock, you can consider our 82-238. I believe this is a match for what you have.