Missing Part

I'm not sure what it is you're referring to. Are you talking about the keeper? If so, these are sold separately. The reason for this is because multiple keepers could be compatible with any one lock. For example, your mortise lock resembles our 82-218, but there are multiple different keepers that are compatible for this, and all of them depend on what kind of space is available in your door. I would start with our 89-020, 89-021, or 89-021D. Carefully compare these to the old keeper to confirm the best match.