Width is how wide the tips are, for instance, needle nose pliers, verses duckbill pliers.
The width is measured parallel to the plier rivet, across the internal surface of the plier jaws.
The width stays constant when the plier jaws are opened.
Thickness, is measured perpendicular to the flats of the jaws.
This is the measurement that “expands” as the plier jaws are opened.
For instance, the “T2” measurements, should be considered the “Tip Width”,
and the “W4” measurement, should be considered the “Tip Thickness”, for this particular pair of plier models.
It might be easier to download the Knipex catalog rather than looking up individual models.
Knipex doesn’t include the same dimensional information for all plier models.