The APU trimming shears / mitre cutting shears are used for working on the various plastic profiles and cutting them to length.
The large trimming shears with supporting surface (Z10) enable you to cut larger profiles (e.g., W66) to the precise size. The mitre cutters (Z11) enable the profiles in corner areas to be cut to the precise mitre. Using the small trimming shears with supporting surface (Z12), smaller profiles can be correctly cut to length.