You get a wooden slingshot model, that is, a solid model of the brass slingshot you want to cast, and then you get 10 pieces of wood, five of which are spliced into a square box with one end open, and 10 pieces can be made into two pieces. Then you first lay a box with sand, press the porcelain (that is, press the sand tightly to make it airtight), put the wooden slingshot in the middle position, then put it in the box above, and put the glue.

This is the principle!

These words are typed in vain! ! !