Nut & Bolt

The NutAndBoltFastener fastener penetrates through all the given parts with the same diameter hole for the bolt to pass through.

The bolt sticks out the end of the last Part, with the nut attached.

import cqparts
from cqparts.constraint import Fixed, Coincident
from cqparts_fasteners.fasteners.nutbolt import NutAndBoltFastener
from cqparts_misc.basic.primatives import Box

class Thing(cqparts.Assembly):
    def make_components(self):
        base = Box(length=20, width=30, height=15)
        top = Box(length=40, width=20, height=5)
        return {
            'base': base,
            'top': top,
            'fastener': NutAndBoltFastener(parts=[base, top]),
        }

    def make_constraints(self):
        base = self.components['base']
        top = self.components['top']
        fastener = self.components['fastener']
        return [
            Fixed(base.mate_bottom),
            Coincident(top.mate_bottom, base.mate_top),
            Coincident(fastener.mate_origin, top.mate_top),
        ]

thing = Thing()

Resulting in:

thing = Thing()
display(thing)

FreeCAD’s render may be more clear (literally).