3pt align will adjust position, rotation and scale of an object in the current 3ds Max scene to align a set of three source points to a second set of three target points.
To use, select any object, then invoke the macro. Next, you pick three source points (A1...A3) in the viewport (you might want to turn on vertex snap while doing so); then you select three target points (B1...B3).
The selected object will be now be transformed in 3D space in such a way that
* point A1 and Point B1 will coincide,
* point A1..A3 will lie in the same plane as Point B1..B3, and
* the line A1-A2 will be parallel to the line B1-B2.
After you have picked the last point, a dialog will open which allows further modifications:
* you can flip the orientation of the alignment,
* you can shift the aligned object along the alignment plane's normal (z axis), and
* you can apply a (uniform) scaling of the object around the point A1 (or have it computed automatically based on the distance between A1 and A2)