Bonsai Knob Cutter by Yoshiaki Tools
Knob Cutters are designed for removing unsightly knobs from trunks and branches without leaving protruding callous when the cut heals. They can also be used to further hollow out the cut after a concave branch cutter is used.
Though not usually a beginner's tool, most serious bonsai enthusiasts wouldn't be without one.
7" (178mm) Made in Japan by Yoshiaki tools