Just like the LEGO bricks, you can create a joint between the two parts. The small, cylindrical bumps on top of most LEGO bricks are called studs. Likewise, you can add a cylindrical object and merge it to either the hair or the head component. Meanwhile, use a slightly larger cylindrical object to tap a hole on another one. However, high precision is required to produce an interference fit. It often takes several times to test and adjust the tolerance for 3D printed parts, to make it work. Joint making will be covered later in the series; however, it won't be used here.