PK 9 is mentioned in different books as one of Poul Kjærholm's most essential chairs, and if you do a little research it makes perfect sense. An important element in Kjærholm's design is the clarity and visibility of the object's connections. Here the Allen screws, developed around 1910 for heavy machinery, are an essential component. In this way the chair's joints became visible and the small industrial screw played an aesthetic role in itself. As the architecture writer Michael Sheridan says:

“The combination of leather and steel with fiberglass and Allen screws mark the PK 9 as the embodiment of the contrasting methods in Kjærholm's conception of furniture”.