Hier wird beschrieben, wie ein Modell, das eine Rotation im Raum hat, mit einer Fläche parallel zu einer Achse ausgerichtet werden kann.

There are two likely scenarios if an object is rotated in Blender.

1) zeroing object rotation.

In this case the cube is off it's axis, we can open the „Item tab“ from the right-side toolbar and see exactly what degree of rotation each axis has.

In this case, a value of 0 can be entered to remove the rotation of each axis.

2) complex rotation

In this case, the degrees of rotation will already show 0, and the object is already rotated.

As we can see in the window on the right, the axes are zeroed out, but the object is rotated.

To solve this, a work-around is needed. Add an empty (shift + A). An empty is an invisible object which is used for cases where scene location and rotation are needed, such as in this case.

With the empty now in the scene, turn on snapping (see topmost arrow), then select edge mode, and turn on „align rotation to target“.

With snapping on, select the empty, press G to move it, and it will snap to the edges of the object. Note in the top right window, the rotation values now show for the empty. These will be „shared“ with the object.

To „share“ the rotational values, select the object, hold shift and select the empty, then press Ctrl+P to parent the object to the normal. Click „set parent to object“.

Note here that the empty hasn't snapped perfect along all axes- so we can zero out 2 axes first.

Note that the rotation values for X and Y are zeroed. Because the empty was rotated on that axis when we snapped it to the object.

With the object selected, press alt+P and cloose „clear parent and keep transformations“. This will tranfer the rotation values to the object, while un-linking them.

Snap the empty to a top edge, so to get an accurate Z value. Then repeat the process of parenting and rotating. The number shown here is 168 degrees, which it shows because the empty flipped on it's Z axis while snapping. This doesn't matter, it can still be zeroed and then flipped 180 degrees again (if model is now facing the wrong direction).

Clear the parent again with Alt+P, and keep transform. The empty can be deleted now, and the object can be aligned as needed.