For this job, we were tasked with fixing back loose doorknob. The customer needed it repaired quickly, as the apartment had to be handed back within the next few days. To complicate matters, this lock model is relatively rare in the market, and would also be extremely expensive to replace. A lockset like this typically costs around a few thousand dollars.
We dismantled the lock handles, as shown in Panel 2, and soon found out that a vital doorknob part had broken into two. Thankfully, a new replacement for the part could be found. With it, we were able to fix it back. The last panel shows the newly repaired doorknob in place.
In addition to fixing back loosened doorknobs, we also fix back lever handles. If the lock design allows it, we are also able to replace doorknobs with lever handles.