The replaced string

The technician was dexterous, guiding the new string through a space I could barely see. She was systematic, checking the neighbouring strings before closing the case. I had expected the visit to end when the broken part was replaced. Instead, the repair was followed by a series of small checks. Each one tested how the new piece behaved as part of the instrument rather than treating it as an isolated object.

From the passage, select two words or phrases that describe the technician's practical skill and organised approach.