Function thicken 

pub fn thicken(
    part: &mut NamedModel,
    namer: &Namer,
    sheet: ShellId,
    thickness: Scalar,
    along_normal: bool,
) -> GeopResult<SolidId>

Thickens the sheet sheet of part into a solid of walls thickness thick — against its faces’ normals, or along them if along_normal — and returns it: the sheet shelled (see the module docs), which replaces it and is named namer’s root.

The sheet’s faces, edges and vertices keep their names, their inner copies are named as shell names them, and along a free edge E of the sheet the wall is N(E,side), with N the operation, the straight edge from a vertex V of it to its inner copy N(V,side).