Cuts made with sharp pruning shears will not bruise the vine and will leave a clean, smooth surface without any loose fibres. Otherwise, the vine will dry out beneath the cut surface, and nearby buds or the sap flow will suffer damage.
Depending on the pruning technique, cuts into the previous year's wood are made about 1-2 cm beyond the last eye (counted from the base of the cane). The short stub left beyond the last eye prevents the latter from drying out... in order to heal, the vine will grow only a cork-like skin or callus over the cut. Leaving stubs longer than 2 cm is not recommended either, as they easily become hiding places for all kinds of uninvited pests. Making the cuts at a slight angle ensures that during the "bleeding," the sap will not flow onto the buds below and "drown" them.
Thick parts of the stem framework are cut back to leave a protrusion approx. 2-5 mm from the main trunk so that the lignification does not grow too deeply into the trunk's sap flow cross-section. Smaller shoots and water shoots are cut flush with the stem.