Shoucolate

I seem to remember reading a translation of an interview/note in which Horikoshi mentioned how Dabi's staple were iconic and this reflected in his clothes too but I can't find it at the moment so I can't check if I can find the Japanese text and what it exactly said.

I do know the Japanese fandom, to talk about them calls them 'STAPLE' (ステープル) or 'HOTCHIKISU hari' (ホッチキス針 "stapler's pin") or 'HOCHIKISU ato' (ホチキス跡 "staple marks/signs") and I do know there are multiple instances in which Touya's face/skin is referred as a 'TSUGIHAGI' (ツギハギ/継ぎ接ぎ "patchwork"), the implication being those staples hold it together in a way that is similar at how Delores, Beetlejuice's soul-sucking ex-wife, stapled her dismembered body parts back together using an industrial stapler, leaving visible, thick staple stitches throughout the film.

It is also worth mentioning Frankenstein's monster in some movies also had staples (this time they are likely surgical staples) holding it together and Touya's look was also inspired to Frankenstain.

Anyway, are Touya's staples 'piercing staples'' or 'surgical staples'?

I don't know.

The color doesn't help as both types can be silver (like in the anime) or gold (like in Horikoshi's illustrations) in color.

We know that after the first war Dabi switched the position of the ones on his hand as the burns on it increased. Since both surgical and piercing staples need to be set by professionals they are likely fictional staples that can be and can do whatever you want.

Still, since those staples have the purpose to hold together Touya's skin, I guess I would more likely go for surgical staples than for piercings, as piercings have more an aesthetic purpose, while he has them because he needs them for a purpose.

On the other side the image on chap 300, when he is starting on moving them, might even be of him holding a piercing...

...though the image is unclear and it might be me seeing things, mixing up lines that are meant to represent something else since either Horikoshi forgot to blacken a part of the image or Touya's hand is drawn wrong or he is holding something bigger than a staple/piercing.

The anime doesn't help as he is holding nothing in it, just touching his own hand.

So who knows? Maybe they are all ring piercings like the ones in his ears. Maybe they are staple piercings. Maybe they are surgical staples. Maybe they are just staples which would be much easier to find than the ones mentioned above.

I couldn't really find a canon source I can't really tell you what they should be. If someone has more info I would apprecciate it if they were to share them with me!