Function solid_from_sheets 

pub fn solid_from_sheets(
    sheets: &[BrepSolid],
    tolerance: f64,
) -> Result<BrepSolid, KernelRefusal>

The solid sheets bound: their faces joined along the edges that coincide within tolerance (the kernel’s sewing, crate::sew_solid, which pairs edges by where they lie and needs no agreement between the sheets’ normals), then turned outward.

One closed face is a solid by itself (a ball’s or a ring’s face from face_from_surface). Refuses sheets that leave an edge open after sewing, saying how many, and a joined body the kernel’s validation rejects.