@Xitel
Those are 鳥口 (toriguchi), or anvil stakes, the naming comes from how the stakes resemble a bird's beak. The literal kanji would be 鳥 (bird) 口 (mouth). It's a tool used in Tsuiki Copperware (the technique) to help shape and contour the copper plate. There are hundreds of different kinds of toriguchi, the artisan would select a couple that are best for the product they are trying to make. Sometimes, the artisans would make the toriguchi themselves for the optimal adherence desired.
As you can see in the image above, the pointy ends of the stakes are the highlight, they serve for both technical and decorative use. In the initial stages, it's mainly for shaping and securing the balance. For the final touches, they may be used to raise the edges for finer details.