The driving gear and the driven gear are respectively provided with an open groove, and the glass sheet is fixed onto the open groove.

Compared with the thyroid gland of grey mullet, the endostyle of amphioxus is primitive. It is an open groove and has lots of cillia adjacent to the pharynx lumen.

Hollow shaft type high pressure cooling system is used to solve the problem in deep drilling, as well as gun-drill with open groove, proper cutting consumption and single tool withdraw are applied.